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Correct option is B. 2

Given∶

Ratio of invested sum = 25 ∶ 15 ∶ 29

Total profit at the end of the year = Rs. 22,977

X = 22977/69 = Rs. 333

∴ Required difference = Rs. (25x – 15x) = Rs. 10x → Rs. 10 × 333 = Rs. 3330

(d) he is a hard taskmaster.

Given∶

Madan invested (3/5)th of the total investment.

Rais’ investment = Ahmad's investment

Ahmad got Rs. 234 as a profit .

Formula used∶

Basic knowledge of ratio and proportion.

Calculation∶

Let the total investment = x

Madan’s investment = (3/5)x

Rest of investment = x – (3/5)x = (2/5)x

According to the question, 

Rais’ investment = Ahmad's investment

So, the investments by Rais and Ahmad are (x/5), each.

So, from the value of Ahmad's share in the profit, we have:

⇒ x/5 = 234

⇒ x = 234 × 5 = 1170

∴ The value of total profit is Rs.1170

 (d) Required selling price

(100/85x837.25) Rs.=985Rs.

Given:

Cost price of 6 articles = Rs. 1

Selling Price of 3 articles = Rs. 1

Formula used:

Profit = SP – CP

Profit percentage = (P/CP) × 100

Here CP is cost price, SP is selling price and P is profit

Calculation:

CP of 1 article = Rs. 1/6

SP of 1 article = Rs. 1/3

Profit = SP – CP 

⇒ Profit (P) = 1/3 – 1/6 = 1/6

Profit percentage = (P/CP) × 100

⇒ P% = [(1/6)/(1/6)] × 100

⇒ P% = 100%

∴ The shopkeeper will earn profit of 100%

Ans: 3

Given:

Cost price for one pen is = 28 Rs.

Selling price for one pen is = 40 Rs.

Formula used:

Calculation:

Cost price for one pen is = 28 Rs.

Selling price for one pen is = 40 Rs.

difference between selling price and cost price = 40 - 28 = 12 Rs.

profit percent = \(\frac{{12}}{{28}}\) × 100 = 42.85%

∴ Profit percent for the shopkeeper is 42.85%.

Given:

Each discount = 20%

Single discount = Rs. 331.20

Concept used:

Using the concept of percentage.

Calculation:

Let the MP is Rs. x.

1st discount at MP = (100 – 20)% of x

⇒ 1st discount = 80% of x

⇒ 1st dicount = 80/100 × x

⇒ 1st dicount = 0.8x

2nd discount = (100 – 20)% of 0.8x

⇒ 2nd discount = 80% of 0.8x

⇒ 2nd dicount = 80/100 × 0.8x

⇒ 2nd dicount = 0.8 × 0.8x

⇒ 2nd dicount = 0.64x

Equivalent discount = x – 0.64x

⇒ 331.20 = 0.36x

⇒ x = 331.20/0.36

⇒ x = Rs. 920

∴ The marked price of an article is Rs. 920.

Given:

Marked price = Rs. 400

Two successive discount = 10%, 15%

Selling price = Rs. 400

Formula used:

S.P. = M.P. (1 - (Discount%/100))

S.P. = C.P. + Profit

Gain % = ((S.P. - C.P.)/C.P.) × 100

Calculations:

Here, M.P. = 400

⇒ Cost price for barish = (400 × (1 - (10/100)) × (1 - (15/100))) + 14

⇒ Cost price for barish = ((400 × 90 × 85)/(100 × 100) ) + 14

⇒ Cost price for barish = 306 + 14

⇒ Cost price for barish = 320

⇒ Gain % = ((400 - 320)/320) × 100 = 25%

∴ Gain % is obtained to be 25%

Given:

Initial discount = 15%

Additional discount = 8%

Final price = Selling price = Rs. 1,564

Concept used:

Selling price = Markup price × (100 - discount percentage)/100

Calculation:

Let the markup price be Rs.x

Selling price when 15% discount is given = x × (100 - 15)/100

⇒ 85x/100

⇒ 0.85x

After giving an additional discount of 8% on discounted price, now the selling price = 0.85x × (100 - 8)/100

⇒ 0.85x × 92/100

⇒ 0.782x

According to the question, Selling price = Rs. 1,564

⇒ 0.782x = 1,564

⇒ x = 1564/0.782

⇒ x = Rs. 2000

∴ The markup price is Rs. 2000    

Given:

Profit while purchasing = 25%

Profit while selling = 10%

Formula used:

Gain percent = [(SP – CP)/100] × 100

Calculation:

Let the CP of 1000 gm of the article be Rs. 1000

According to the question,

The shopkeeper gets a profit of 25% while buying

⇒ He buys 1000 + (25/100) × 1000 = 1250 gm of goods for Rs. 1000

He cheated to 10% while selling the goods

⇒ He sells 1000 – (10/100) × 1000 = 900 for Rs. 1000

⇒ He gets a profit of 1250 – 900 = 350 gm

⇒ Overall profit = (350/900) × 100 = 38.88%

∴ The overall profit is 38.88%

Given:

List price of the a bike is more than it's cost price = 15%

Discount % = 20%

Formula:

If a number is increase by x%, then

Increased number = Actual number × (100 + x)/100

SP = MP × (100 - Discount%)/100

Loss = CP – SP

Loss % = (Loss/CP) × 100 

Calculation:

Let cost price of bike be Rs. 100, then

List price of the bike = 100 × (115/100) = Rs. 115

SP of the bike = 115 × (80/100) = Rs. 92

Loss = Rs. 100 - Rs. 92 = Rs. 8 

∴ Loss% = (8/100) × 100 = 8%

Given:

Successive discount% = 15% and 10%

Marked price of washing machine = Rs.20,000

Concept used:

If two successive discount percent is x% and y%

Then, Effective discount% = x + y – (xy/100)

Selling price = Marked price – Discount

Calculation:

Effective discount% = 15 + 10 – {(15 × 10)/100}

⇒ 23.5%

Discount = Rs. 20, 000 × (23.5/100)

⇒ Rs.4,700

Selling price = Marked price – Discount

Selling price = Rs. (20000 – 4700)

⇒ Rs.15,300

∴ Selling price of Washing machine is Rs. 15,300

Given:
Discount = 20%
Profit on cost price = 20% 

Concept used:
S.P. = C.P. × (100 + Profit %)/100
Indirect process:-
M.P. = S.P. × 100/(100 – discount %)

Calculation: 
Let the cost price of the articles be 100
Selling price of the articles to get 20% profit  = 100 × (100 + 20)/100 = 120
Loss percentage incurred by selling 16 articles at the cost of 12 articles = (16 – 12)/16 × 100
⇒ 4/16 × 100
⇒ 1/4 × 100
⇒ 25%
Selling price of the articles before allows 16 articles to a dozen = 120 × 100/(100 – 25)
⇒ 120 × 100/75
⇒ 120 × 4/3
⇒ 160
Listed price of the articles before given the 20% discount = 160 × 100/(100 – 20)
⇒ 160 × 100/80
⇒ 2 × 100
⇒ 200
Percentage of listed price marked above the cost price = 100%
∴ 100% above the actual price were his article listed.

Given-

MRP = Rs 1,000

Discounted Special Price = Rs. 979 

Formula Used-

Discount % = (MRP - Discounted Price)/MRP × 100

Calculation- 

Discount % = (1000 - 979)/1000 × 100

⇒ 2.1

∴ Percentage of discount given for that item = 2.1%

Given:

Selling price of blanket = Rs 680

Discount = 15% and 20%

Formula Used:

Printed price = Selling price × [100/(100 – discount%)]

Calculation:

Printed price = Selling price × [100/(100 – discount%)]

⇒ 680 × [100/(100 – 15)] × [100/(100 – 20)]

⇒ 680 × (100/85) × (100/80)

⇒ 1000

∴ The printed price of the blanket is Rs 1000

Given:

Marked price = ₹ 240

Discount = 10% and 5%

Formula used:

Successive discount% = {(x + y) - (x × y)/100}

where, x and y are discount 

Discount = M.P × {(100 - discount%)/100}

S.P = M.P - Discount

Calculation:

Let x be 10% and y be 5%

Successive discount = {(x + y) - (x × y)/100}

⇒ Successive discount = {(10 + 5) - (10 × 5)/100}

⇒ Successive discount = 15 - 0.5 ⇒ 14.5%

Discount = M.P × {(100 - discount%)/100}

⇒ Discount = 240 × {(100 - 14.5)/100}

⇒ Discount = 240 × {(85.5)/100}

⇒ Discount = 205.20

∴ The selling price of the item is ₹ 205.20.

Given:

Total profit = Rs. 7400

A’s investment = Rs. 6500

B’s investment = Rs. 8400

C’s investment = Rs. 10000

Investment time of A = 6 months

Investment time of B = 5 months

Investment time of C = 3 months

Concept Used:

Profit ratio is equal as product of investment and time ratio

Calculation:

Ratio of their investment = (6500 × 6) ∶ (8400 × 5) ∶ (10000 × 3)

⇒ Required ratio = 39000 ∶ 42000 ∶ 30000

⇒ Required ratio = 13 ∶ 14 ∶ 10

Extra profit received by A = 5% of 7400

⇒ Extra profit of A = 5/100 × 7400

⇒ Extra profit of A = 370

Balance profit = 7400 – 370

⇒ Balance profit = 7030

B’s share = 7030 × 14/37

⇒ B’s share = 2660

∴ B’s share is Rs. 2660.

Given:
After 5 years, father's age = 3 × Son's age
5 years ago, father's age = 7 × Son's age

Calculation:
Let 5 years ago, son's age be s.
5 years ago, Father's age = 7 × s = 7s
After 5 years, son's age = s + 5 + 5 = s + 10
After 5 years, father's age = 7s + 5 + 5 = 7s + 10      ----(1)
After 5 years, father's age = 3 × Son's age = 3 × (s + 10)      ----(2)
Equating equation (1) and (2),
⇒ 7s + 10 = 3s + 30 
⇒ 7s – 3s = 30 – 10
⇒ 4s = 20
⇒ s = 20/4
⇒ s = 5
Present age of father = 7s + 5
⇒ 7 × 5 + 5
⇒ 35 + 5 = 40
∴ The present age of the father is 40 years.

Given:

Marked price of earphone (MP_e) = Rs. 750

Marked price of headphone (MP_h) = Rs. 1250

Formula used:

S.P = M.P × (100 – D%)/100

Where

D% → Discount%

S.P. → Selling price

M.P. → Marked price 

Calculations:

S.P of an earphone = 750 × (100 – 8)/100

⇒ 750 × 23/25 = Rs. 690

S.P of a headphone = 1250 × (100 – 20)/100 = 1000 

Total S.P. of 5 earphones and 3 headphones = 5 × 690 + 3 × 1000 = Rs. 6450

Total M.P. of 5 earphones and 3 headphones = 750 × 5 + 1250 × 3 = 7500

Discount = Rs. (7500 – 6450) = Rs. 1050

Discount% = (1050/7500) × 100 = 14%

∴ The required discount% is 14% 

Given:

Age of a man after 17 years is 3 times the age of that man 17 years ago.

Calculation:

Let the present age of man be x years

According to the question,

x + 17 = 3(x – 17)

⇒ x + 17 = 3x – 51

⇒ x – 3x = –51 – 17

⇒ –2x = –68

⇒ x = 34

∴ Man’s present age is 34 years.

Given:

Marked price of the product = Rs. 750

Selling price of the product = Rs. 660

Concept used:

Discount % = {(MP – SP)/MP} × 100

MP = Marked price of the product

SP = Selling price of the product

Calculation:

According to the question,

Discount % = {(750 – 660)/750} × 100

⇒ Discount % = (90/750) × 100

⇒ Discount % = 12

∴ Required percentage of discount was 12%

Given:

Ratio of efficiency of A, B and C = 9 : 10 : 12

Time taken by them to finish the job working together = 3 days

Formula used:

Total work = work done rate × time

Calculations:

Let us assume, efficiencies of A, B and C are 9x, 10x and 12x respectively.

Working together, amount of work done by them/day = (9x + 10x + 12x) = 31x

Total work = 31x × 3 = 93x

If A works alone, time required to finish = 93x/9x = 31/3 days

If B works alone, time required to finish = 93x/10x = 93/10 days

If C works alone, time required to finish = 93x/12x = 93/12 days

Required ratio = 31/3 : 93/10 : 93/12 = 1/3 : 3/10 : 3/12 = 20 : 18 : 15

Given:

Ratio of efficiency of Ullas to Tejas = 2 : 1

Time to complete the whole work together = 18 days

Formula used:

Efficiency = (Total work)/(Time Taken)

Calculations:

Let the efficiency of Ullas and Tejas be 2 units/day and 1 unit/day respectively.

Combined efficiency of Ullas and Tejas together = 2 + 1 = 3 units/day

Efficiency = (Total work)/(Time Taken)

⇒ 3 = (Total work)/18

⇒ Total work = 54 units

Time to complete the whole work by Tejas alone = 54/1 = 54 days

∴ Tejas will complete the same work alone in 54 days.

Given:

3 men, 4 women, and 5 boys can complete work in 47 days

Calculation:

3 men, 4 women, and 5 boys can complete work in 47 days

\( \Rightarrow \frac{{47}}{{\frac{1}{3}\; + \;\frac{1}{4}\; + \;\frac{1}{5}\;}}\)

\( \Rightarrow \frac{{47}}{{\frac{{20 + 15 + 12}}{{60}}\;}}\)

⇒ (47/47) × 60

⇒ 60 days

Given:

Length of the train = 600 m

Length of platform = 1200 m

Speed of the train = 180 km/hr = (180) × (5/18) m/s

⇒ 50 m/s

Formula used:

Time taken = Total distance covered/Speed of the train

Calculation:

Total distance covered = (600 + 1200) m

⇒ 1800 m

Time taken = (1800/50) seconds

 ⇒36 seconds

∴ Time taken to cross the platform is 36 seconds

Given:

The speed of train = 72 km/hr

The length of platform = 500 m

The speed of another train = 108 km/hr

Formula used:

Distance = speed × time

Concept used:

To convert speed from km/hr to m/s the multiply with 5/18 

Relative speed concept,

Speed of both trains will add when the train moves in the opposite direction

Speed of both the train will subtract when the train moves in the same direction

Calculation:

Let the length of train be l 

Now, Distance = speed × time 

⇒ l + 500 = 72 × 5/18 × 120

⇒ l = 1900 m

The total length of both the train = 2 × 1900 = 3800 m

Both trains moving in the opposite direction so speed = (20 + 30) = 50 m/s

Time = 3800/50 = 76 second

∴ The time taken to cross another train is 76 seconds

Given:

10 Men in 5 days earned Rs. 800

Women are twice as efficient as men 

Concept used:

If x person in n days earn Rs. y, then 1 person will earn in 1 day Rs y/(x × n) 

Calculation:

10 men earned in 5 days = Rs. 800

1 man will earn in 1 day = 800/(5 × 10)

1 man will earn in 1 day = 160/10 = Rs. 16

As women are twice as efficient as men so woman will earn twice of what man would earn.

1 woman will earn in 1 day = 2 × 16 = Rs. 32

5 woman will earn in 10 days = 5 × 10 × 32 = 1600

∴ 5 woman will earn Rs. 1600 in 10 days

Given:

Number of men = 10

Number of days = 5

Wages = Rs. 6000

Formula used:

If ‘M₁’ person can do work in ‘D₁’ days and there are wages₁ and ‘M₂’ persons can do work in ‘D₂’ days and there are wages₂, then

M₁D₁/Wages₁ = M₂D₂/Wages₂

M₁, M₂, D₁, D₂ are the number of men and the number of days

Calculation:

M₁ = 10; Wages₁ = Rs. 6000, D₁ = 5; M₂ = 6; Wages₂ = Wages₂ and D₂ = 7

⇒ (10 × 5)/6000 = (6 × 7)/Wages₂

⇒ Wages₂ = (6 × 6000 × 7)/(10 × 5)

⇒ Wages₂ = Rs. 5040

∴ 6 men earn Rs. 5040 in 7 days.

Given:

Number of men = 8

Number of days = 10

Wages = Rs. 640

Formula used:

M1D1/Wages1 = M2D2/Wages2  

M1, M2, D1, D2 are number of men and number of days  

Calculation:

M1 = 8; Wages1 = Rs. 640, D1 = 10; M2 = 15; and D2 = 5

⇒ (8 × 10)/640 = (15 × 5)/wages2

⇒ Wages = (15 × 640 × 5)/(8 × 10)

⇒ Wages = Rs. 600

Given∶

Number of men = 25

Number of days = 4

Wages = Rs. 64000

Formula used∶

M₁D₁ / wages₁ = M₂D₂ / Wages₂

M₁, M₂, D₁, D₂ are number of men and number of days

Calculation∶

M₁ = 25; Wages₁ = Rs. 64000, D₁ = 4; M₂ = 8; Wages₂ = wages₂ and D₂ = 8

⇒ (25 × 4) / 64000 = (8 × 8) / wages₂

⇒ Wages = (8 × 64000 × 8) / (25 × 4)

⇒ Wages = Rs. 40960

∴ 8 men earn Rs. 40960 in 8 days.

Given:

P's 1 day's work = 1/10

Q's 1 day's work = 1/40

(P + Q)'s 2 days work = 1/10 + 1/40 = 1/8

(P + Q)'s 4 days work = 2 × 1/8 = 1/4

Similarly,

(P + Q)'s 16 days work = 8 × 1/8 = 1

Ratio of their work done = 8/10 : 8/40 = 4/5 : 1/5 = 4 : 1

∴ Profit share of P = 4/5 × 900 = Rs.720

Given:

Speed of train = 108 km/hr

Length of train = 120 metre

Detailed solution:

108 km/hr = (108×5)/18 metre/sec

⇒ 30 m/sec

Time taken by train to cross an electric pole will be.

⇒ 120/30

⇒ 4

∴ Time taken by train to cross the pole is 4 seconds

Given

Train crosses a platform of 200 m long in 90 seconds

Speed of train = 60 km/hr.

Concept

Speed = (Distance/Time) 

Speed in meter/second = (5/18) km/h

When a train cross a pole it means the length of train is actual distance.

Calculation 

Let the length of train be x meter

Total distance covered by train = length of train + length of platform 

⇒ Total distance covered by train = (x + 200) m.

⇒ Speed of train in meter per second = (5/18) × 60

⇒ Speed of train in meter per second = (50/3) m/s

⇒ (50/3) = (x + 200)/90

⇒ (50 × 90)/3 = x + 200

⇒ 1500 = x + 200 

⇒ x = 1500 - 200 

⇒ x = 1300 meter 

Length of train = 1300 meter 

Now,

⇒ The time taken by the train to cross an electric pole = (1300/(50/3))

⇒ The time taken by the train to cross an electric pole = 78 sec.

∴ The time taken by the train to cross an electric pole is 78 sec.

Given:

Total earning = Rs. 16000

Arun do (1/5)th of a work

Calculation:

Let total work = 1

Work done by Karuna = 1 – (1/5) = 4/5

Karuna's share = (4/5) × 16000 = Rs. 12,800

Given:

Speed \(=\left(45 \times \dfrac{5}{18}\right)\) m/sec \(=\left(\dfrac{25}{2}\right)\) m/sec

Time = 30 sec.

Formula Used:

 Distance = Speed × Time

Calculation:

Let the length of bridge be x metres.

\(\dfrac{10+x}{30}=\dfrac{25}{2}\)
⇒ 2(130 + x) = 750

⇒ x = 245 m.

Conclusion:

Length of bridge will be 245 metres

Given: 

Length of train = 280 m, and length of bridge = 70 m

Concept: 

When speed is constant, the ratio of time is equal to the ratio of distance

Calculation: 

When train crosses an electric pole, then

The distance covered by train = 280 m

When train crosses a bridge, then

The distance covered by train = 280 + 70 = 350 m

Now, 

The ratio of time taken by a train crosses an electric pole and a bridge

⇒ 280 : 350

⇒ 4 : 5

∴ The required ratio is 4 : 5. 

Given:

Length of the train is 200 m and the length of the bridge is 250 m. Speed of the train is 45 m/s

Concept Used:

To cover the bridge = To cover the sum of the length of the bridge and train

Time = Distance/speed

Calculation:

Speed of the train is 45 m/s

To cross the bridge the train, have to cover a distance of (200 + 250) = 450 m

Required time = 450/45  

⇒ 10 second

∴ Time taken by the train to cross a bridge of length 250 m is 10 second.

Given:

Distance covered downstream = 20 km

Distance covered upstream = 28 km

Speed of boat in still water = 7 km/hr

Speed of stream = 3 km/hr

Concept used:

Downstream speed = Speed of boat in still water + Speed of stream

Upstream speed = Speed of boat in still water – Speed of stream

Calculation:

Downstream speed = (7 + 3) km/hr

⇒ 10 km/hr

Upstream speed = (7 – 3) km/hr

⇒ 4 km/hr

Time taken to cover 20 km downstream = 20/10 hours

⇒ 2 hours

Time taken to cover 28 km upstream = 28/4 hours

⇒ 7 hours

Total time taken to complete the whole journey = (2 + 7) hours

⇒ 9 hours

∴ The time taken to complete the whole journey is 9 hours

Given:

Speed of a boat in still water is 9 km/hr

Speed of the stream is 3 km/hr.

Concept Used:

Upstream Speed = Speed of boat - Speed of stream

Downstream Speed = Speed of boat + Speed of stream

Calculation:

Upstream Speed = Speed of boat - Speed of stream

⇒ Upstream Speed = 9 - 3

⇒ Upstream Speed = 6 km/hr

Downstream Speed = Speed of boat + Speed of stream

⇒ Downstream Speed = 9 + 3 

⇒ Downstream Speed = 12 km/hr

Difference between the upstream speed and downstream speed 

⇒ 12 - 6

⇒ 6 km/hr

∴ Difference between the upstream speed and downstream speed is 6km/hr.

Given:

Upstream speed = 8 km/hr

Downstream speed = 10 km/hr

Formula Used:

Speed = Distance/Time

D = B + S

U = B - S 

where, D → Downstream speed, U → Upstream speed, B → Speed of boat in still water, S → Speed of stream.

Calculations:

D = B + S

⇒ B + S = 10      ----(1)

Similarly, U = B - S

⇒ B - S = 8      ----(2)

Using componendo-dividendo, we get

(B + S) + (B - S)/(B + S) - (B - S) = (10 + 8)/(10 - 8)

⇒ B/S = 9/1

⇒ B : S = 9 : 1

∴ The ratio of speed of stream to speed of boat in still water is 1 : 9

Calculation:

Anil, Sunil and Bimal together finished the job

Bimal has done 10% of the job

⇒ Job done by Anil and Sunil = (100% – 90%) of the job

⇒ 90% of the job

Total job is the LCM of 20, 40

⇒ 40

Efficiency of Anil = 40/20

⇒ 2

The efficiency of Sunil = 20/20

⇒ 1

Let the number of days Anil and Sunil done the job together be D days

Anil has done the job alone for three days and then Sunil joined him and they have together done the job

⇒ 2 × 3 + D(2 + 1) = 90/100 × 40

⇒ 3D = 36 – 6

⇒ D = 30/3

⇒ D = 10

Total time to complete the job = D + 3

⇒ 13 days

∴ In 13 days the job was done.

Given:

⇒ Speed upstream = 35/7 = 5kmph

⇒ Speed of stream = 20kmph

⇒ Speed of boat in still water = 20 + 5 = 25 kmph

⇒ Speed downstream = 25 + 20 = 45 kmph

∴ Required time = 45/45 + 20/5 = 5 hours

Given:

The upstream speed of a boat is 15 kmph and it travels a distance of 110 kms in 2 hours during downstream.

Formula:

Time taken by boat to travel upstream = D/(speed of bota in still water – speed of the stream)

Time taken by boat to travel downstream = D/(speed of bota in still water + speed of the stream)

Calculation:

The upstream speed of a boat is 15 kmph

Downstream speed = 110/2 = 55 kmph

Required time = 165/15 + 165/55 = 11 + 3 = 14 hours

Given:

A can do a piece of work in 20 hours 

B can do same work in = 24 hours 

A, B, and C working together can do the same work in = 8 hours

Concept Used:

If a man can do a work in x hours then he will do 1/x part of the work in 1 hour.

Calculation:

Work done by A in 1 hour = 1/20

Work done in 1 hour = 1/24  hour

Work done by A, B, C together in 1 hour =18

We know that, 

Work done by C in 1 hour = work done A, B, and C in 1 hour-work done by A and B in 1 hour

⇒ \(\frac{1}{8} - \left( {\frac{1}{{20}} + \frac{1}{{24}}} \right)\)

⇒ \(\frac{1}{8} - \frac{{11}}{{120}}\)

⇒ (15 - 11)/120    (by taking LCM for 8and 120 which is 120 

⇒ \(\frac{4}{{120}}\)

⇒ 1/30 

∴ C complete the work is 30 hours

Calculation:

Let Ena's age be 'x'

Last year Ena's age is equal to the square of a number

⇒ x - 1 = n²      ----(1)

After 1 year age is equal to the cube of the number

⇒ x + 1 = m³      ----(2)

Last year and Next year are 2 years apart, so we have to find the square and cube with a difference of 2.

Squares of numbers = 1, 4, 9, 16, 25, 36, 49, 64,.....

Cubes of numbers = 1, 8, 27, 64, 125, 216,....

Add 2 in squares of numbers = 3, 6, 11, 18, 27, 38, 51, 66, ....

We can notice 27 cubes only we are getting after adding 2

Current age of Ena's = 25 + 1 = 26 years

27 is the cube of 3³ = 27 and next cube is 4³ = 64

Ena's has to wait = 64 - 26 = 38 years

∴ Ena's has to wait 38 years.