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201.

Add the following rational numbers:(i) \(\frac{-5}{7}\; and\; \frac{3}{7}\)(ii) \(\frac{-15}{4} \;and\;\frac{7}{4}\)(iii) \(\frac{-8}{11}\;and\;\frac{-4}{11}\)(iv) \(\frac{6}{13}\;and\;\frac{-9}{13}\)

Answer»

All denominators are in positive numbers. We add it

i) \(\frac{-5}{7} +\frac{3}{7}=\frac{(-5 + 3)}{7}=\frac{2}{7}\)  

ii) \(\frac{-15}{4} + \frac{7}{4}=\frac{(-15+7)}{4}=\frac{-8}{4}\)

\(\frac{-8}{4}=-2\) (Dividing by 4 we get)

iii) \(\frac{-8}{11}+\frac{-4}{11}= \frac{-8+(-4)}{11}=\frac{-12}{11}\)

iv) \(\frac{6}{13} +\frac{-9}{13}= \frac{6+(-9)}{13}=\frac{-3}{13}\)

202.

Add the following rational numbers:(i) \(\frac{3}{4}\) and \(\frac{-5}{8}\)(ii) \(\frac{5}{-9}\) and \(\frac{7}{3}\)(iii) -3  and \(\frac{3}{5}\)(iv) \(\frac{-7}{27}\) and \(\frac{11}{18}\)(v) \(\frac{31}{-4}\) and \(\frac{-5}{8}\)(vi) \(\frac{5}{36}\) and \(\frac{-7}{12}\)

Answer»

i) The denominators are 4 and 8 . The LCM of 4 and 8 is 8.
We rewrite the given fraction in order to get the same denominator

\(\frac{-3}{4}=\frac{(3\times2)}{(4\times2)}=\frac{6}{8}\) and \(=\frac{-5}{8}\)

\(\frac{-5}{8}=\frac{(-5\times1)}{(8\times1)} \)

Hence the denominators are same.Now,

\(\frac{6}{8}+\frac{-5}{8} \)

\(\frac{6+(-5)}{8}=\frac{(6-5)}{8}\)

\(\frac{1}{8} \)

ii) We convert the denominators in to positive numbers

\(\frac{5}{-9} =\frac{(5\times-1)}{(-9\times-1)}\)

\(\frac{-5}{9}\)

The denominators are 9 and 3.The LCM for 9 and 3 is 9
We rewrite the given fraction in order to get the same denominator.

\(\frac{-5}{9}=\frac{(-5\times1)}{(9\times1)}\)

\(\frac{-5}{9}\) and \(\frac{7}{3}\)

\(=\frac{(7\times3)}{(3\times3)}\)

\(\frac{21}{9}\)

Since the denominators are same now we can add them directly.We get

\(\frac{-5}{9}\) + \(\frac{21}{9}=\frac{(-5+21)}{9}\)

\(\frac{16}{9}\)

iii) The denominators are 1 and 5.The L.C.M of 1 and 5 is 5.
We rewrite the given fraction in order to get the same denominator.We get

\(\frac{-3}{1}=\frac{(3\times5)}{(1\times5)}\)

\(\frac{-15}{5}\) and \(\frac{3}{5}\)

\(=\frac{(3\times1)}{(5\times1)}\)

\(\frac{3}{5}\)

Since the denominators are same now we can add them directly.We get

\(\frac{-15}{5}+\frac{3}{5}=\frac{(-15+3)}{5}\)

\(\frac{-12}{5}\)

iv) The denominators are 27 and 18. The L.C,M of  27 and 18 is 54.
We rewrite the given fraction in order to get the same denominator.We get

\(\frac{-7}{27}=\frac{(-7\times2)}{(27\times2)}\)

\(\frac{-14}{54}\) and \(\frac{11}{18}\)

\(=\frac{(11\times3)}{(18\times3)}\)

\(\frac{33}{54}\)

Since, the denominators are same we can add them directly

\(\frac{-14}{54} + \frac{33}{54}=\frac{(-14+33)}{54}\)

\(\frac{19}{54}\)

v) Firstly we  convert the denominators to positive numbers.

\(\frac{31}{-4}=\frac{(31\times-1)}{(-4\times-1)}\)

\(\frac{-31}{4}\)

The denominators are 4 and 8. The L.C.M of 4 and 8 is 8
We rewrite the given fraction in order to get the same denominator. We get

\(\frac{-31}{4}=\frac{(-31\times2)}{(4\times2)}\\=\frac{-62}{8}\) 

\(\frac{5}{8}=\frac{(-5\times1)}{(8\times1)}\\=\frac{-5}{8}\)

Since the denominators are same we can add them directly as

\(\frac{-62}{8}+\frac{(-5)}{8}=\frac{(-62+(-5))}{8}\\\frac{(-62-5)}{8}=\frac{-67}{8}\)

vi) : The denominators are 36 and 12. The L.C.M of 36 and 12 is 36.
We rewrite the given fraction in order to get the same denominator.We get

\(\frac{-5}{36}=\frac{(5\times1)}{(36\times1)}\\=\frac{5}{36}\) 

\(\frac{-7}{12}=\frac{(-7\times3)}{(12\times3)}\\\frac{-21}{36}\)

Now, the denominators are same we can add them directly.We get

\(\frac{5}{36} + \frac{-21}{36}=\frac{(5+(-21))}{36}\\\frac{5-21}{36}=\frac{16}{36}\\\frac{-4}{9}\)

203.

Keeping the place of 6 in the number 6350947 same, the smallest number obtained by rearranging other digits is (A) 6975430 (B) 6043579 (C) 6034579 (D) 6034759

Answer» The correct option is (C) 6034579.
204.

A submarine was situated 450 feet below sea level. If it descends 300 feet. What is its new position?

Answer»

Position of submarine = -450 ft. 

Again it descends 300 feet ⇒ -300 feet

∴ New position = -450 + (-300) = -750 ft. 

∴ It was 750 feet below sea level

205.

Find the sum of the greatest and the least six digit numbers formed by the digits 2, 0, 4, 7, 6, 5 using each digit only once.

Answer»

By using the digits 2, 0, 4, 7, 6, 5

The greatest number formed = 765420, and the least number formed = 204567

∴ The required sum = 765420 + 204567 = 969987

206.

State whether the given statement are true (T) or false (F).Any non-zero whole number divided by itself gives the quotient 1.

Answer»

True.

Consider any non-zero whole number i.e. 5

5 is divided by itself = 5/5 = 1

207.

State whether the given statement are true (T) or false (F).Every number is a multiple of itself.

Answer»

True.

We know that, 1 is the identity for multiplication of whole numbers

Therefore, any number is multiplied by 1 we get the number itself.

Hence, every number is a multiple of itself.

208.

State whether the given statement are true (T) or false (F).Every multiple of a number is greater than or equal to the number.

Answer»

True.

As per the standard rule, every multiple of a number is greater than or equal to the number.

2 × 1 = 2

2 × 3 = 6

209.

State whether the given statement are true (T) or false (F).The number of multiples of a given number is finite.

Answer»

False.

The number of multiples of a given number is infinite.

Because, we know that numbers are infinite.

210.

The sum of first three common multiples of 3, 4 and 9 is (A) 108 (B) 144 (C) 252 (D) 216

Answer»

The correct option is (D) 216.

First we have to find out common multiples of 3 , 4 and 9, 

For that find L.C.M of 3 ,4 and 9 

3 | 3 , 4 , 9

 __________ 

1 , 4 , 3 

L. C.M ( 3 , 4 ,9 ) = 3 × 4 × 3 = 36 

Now multiples of 36 = { 36 , 72 , 108,  ....} 

Sum of first three common multiples of 3 , 4 , and 9 = 36 + 72 + 108 = 216

211.

Fill in the blanks to make the statements true.Length of river ‘Narmada’ is about 1290km. Its length in metres is_______.

Answer»

We know that 1 km = 1000 m 

Length of river ‘Narmada’ is about 1290 km. 

Length of river ‘Narmada’ in metres = 1290 x 1000 m = 1290000 m

212.

A rational number between 2 and 3 is(A) (√2+√3)/2(B) (√2. √3)/2(C) 1.5(D) 1.8

Answer»

(C) 1.5

Explanation:

√2 =1.4142135…. and √3 =1.732050807….

(A) (√2+√3)/2 = 1.57313218497… is a non-terminating and non-recurring decimal and therefore is an irrational number.

(B) (√2. √3)/2 = 1.22474487139… is a non-terminating and non-recurring decimal and therefore is an irrational number.

(C) 1.5 is a terminating decimal and therefore is a rational number.

(D) 1.8 is a terminating decimal and therefore is a rational number.

Here both 1.5 and 1.8 are rational numbers. But, 1.8 does not lie in between √2 =1.4142135…. and √3 =1.732050807…. Whereas 1.5 lies in between √2 =1.4142135…. and √3 =1.732050807….

Hence, (C) is the correct option.

213.

The value of 1.999… in the form p/q, where p and q are integers and q ≠ 0 , is(A) 19/10(B) 1999/1000(C) 2(D) 1/9

Answer»

(C) 2

Explanation:

(A) 19/10 = 1.9

(B) 1999/1000= 1.999

(C) 2

(D) 1/9= 0.111….

Let x = 1.9999….. — ( 1 )

Multiply equation ( 1 ) with 10

10x = 19.9999….. — ( 2 )

Subtract equation (1) from equation(2)

We get,

9x = 18

x = 18 / 9

x = 2

Therefore,

x = 1.9999… = 2

Hence, (C) is the correct option.

214.

The value of 2√3 + √3 is(a) 2√6(b) 6 (c) 3√3(d) 4√6

Answer»

(c) 3√3

2√3 + √3 

= √3 (2 + 1) 

= 3√3

215.

Fill in the blanks to make the statements true.1 centimetre = _____ millimetres.

Answer»

1 centimetre = 10 millimetres.

216.

Write each of the following in numeral form.i) Hundred crores hundred thousands and hundred.ii) Twenty billion four hundred ninety seven million pinety six thousands four hundred seventy two.

Answer»

i) 100,01,00,100.

ii) 20,497,096,472

217.

Fill in the blanks to make the statements true.1 kilometre = _____ millimetres.

Answer»

1 kilometre = 10,00,000 millimetres.

We know that, 1 km = 1000 meters.

1 metre = 100 centimetre

1000 metre = 1000 × 100

= 1,00,000 centimetre

1 cm = 10 millimetres

Then, 1,00,000 centimetre = 10 × 1,00,000 = 10,00,000 millimetres

218.

Fill in the blanks to make the statements true.Height of a person is 1 m 65 cm. His height in millimetres is_______.

Answer»

1 m = 100 cm

1m 65 cm = 100cm + 65 cm = 165 cm

1cm = 10 mm

165cm = 165×10 = 1650 mm

His height in millimeter is 1650mm

219.

Express \(0.6 + 0.\overline7 + 0.4\overline7\) in the form p/q, where p and q are integers and q ≠ 0.

Answer»

Let x = 0.6

Multiply by 10 on L.H.S and R.H.S,

10x = 6

x = 6/10

x = 3/5

So, the p/q form of 0.6 = 3/5

Let y = 0.77777…

Multiply by 10 on L.H.S and R.H.S,

10y = 7.7777…

10y – y = 7.7777777……. – 0.7777777…………..

9y = 7

y = 7/9

So the p/q form of 0.7777… = 7/9

Let z = 0.47777…

Multiply by 10 on L.H.S and R.H.S,

10z = 4.7777…

10z – z = 4.7777777… – 0.47777777…

9z = 4.2999

z ≈ 4.3/9

z = 43/90

So the p/q form of  0.4777… = 43/90

Therefore, p/q form of \(0.6 + 0.\overline7 + 0.4\overline7\) is,

x+y+z = 3/5 + 7/9 + 43/90

= (54 + 70 + 43)/90

= 167/90

220.

Fill in the blanks to make the statements true.10 million = _____ crore.

Answer»

10 million = 1 crore

We know that, 1 million = 10 lakh

Then, 10 million = 10 × 10 = 100 lakh = 1,00,00,000

Therefore, 10 million = 1 crore.

221.

Fill in the blanks to make the statements true.1 metre = _____ millimetres.

Answer»

1 metre = 1000 millimetres

We know that, 1 metre = 100 centimetre

1 centimetre = 10 millimeter

Then, 100 cm = 10 × 100 = 1000 millimetres

222.

Fill in the blanks to make the statements true.100 thousands = _____ lakh

Answer»

100 thousands = 1 lakh

223.

The number of factors of 36 is (A) 6 (B) 7 (C) 8 (D) 9

Answer»

The correct option is (D) 9.

The answer is 9 factors which are 1,2,3,4,6,9,12,18 and 36.

224.

Fill in the blanks to make the statements true.10 lakh = _____ million.

Answer»

10 lakh = 1 million.

225.

State whether the given statement are true (T) or false (F).XXIX = 31

Answer»

False.

Where, X = 10

IX = 9

So, XXIX = 10 + 10 + 9

= 29

226.

The product of the place values of two 2’s in 428721 is (A) 4 (B) 40000 (C) 400000 (D) 40000000

Answer»

The correct option is (C) 400000.

The product of the place values of two 2’s in 428721 is

There are two 2’s in the given number.

So, the first 2 is in the tenth place,

Then, the product is = 2 × 10

= 20

The other 2 is in place value of ten thousand.

Then, = 2 × 10000

= 20000

Therefore, the product of place values = 20 × 20000

= 400000

227.

One million is equal to (A) 1 lakh (B) 10 lakh (C) 1 crore (D) 10 crore

Answer»

(B) 10 Lakh

One million is equal to ten lakh.

1,000,000 = 10,00,000

228.

Find whether the following statements are true or false.(i) Every real number is either rational or irrational.(ii) π is an irrational number.(iii) Irrational numbers cannot be represented by points on the number line.

Answer»

(i) True: As we know that rational and irrational numbers taken form the set of real numbers.

(ii) True: As, is ratio of the circumference of a circle to its diameter, it is an irrational number.

π = \(\frac{2πr}{2r}\)

(iii) False: Irrational numbers can be represented by point on the number line.

229.

State whether the given statement are true (T) or false (F).532235 = 5 × 100000 + 3 × 10000 + 2 × 1000 + 2 × 100 + 3 × 10 + 5

Answer»

True.

Left Hand Side = 532235

Right Hand Side = 5 × 100000 + 3 × 10000 + 2 × 1000 + 2 × 100 + 3 × 10 + 5

= 5,00,000 + 30,000 + 2000 + 200 + 30 + 5

= 5,32,235

Left Hand Side = Right Hand Side

230.

3 × 10000 + 7 × 1000 + 9 × 100 + 0 ×10 + 4 is the same as (A) 3794 (B) 37940 (C) 37904 (D) 379409

Answer»

The correct option is (C) 37904.

3 × 10000 + 7 × 1000 + 9 × 100 + 0 × 10 + 4

= 30000 + 7000 + 900 + 0 + 4

= 37904

231.

If 1 is added to the greatest 7- digit number, it will be equal to (A) 10 thousand (B) 1 lakh (C) 10 lakh (D) 1 crore

Answer»

The correct option is (D) 1 crore.

Greatest 7 digit number is 9999999

When added with 1,

9999999 + 1

= 10000000

= 1 crore

232.

Numbers having more than two factors are called __________ numbers.

Answer»

Numbers having more than two factors are called Composite numbers.

A number that has more factors than itself and 1 is called a composite number because '1' is neither prime nor composite , and its only factor is 1.

233.

State whether the given statements are true or false:LXXV is greater than LXXIV.

Answer»

True 

[LXXV = 75, LXXIV = 74] 

234.

Fill in the blanks to make the statements true.The population of Pune was 2,538,473 in 2001. Rounded off to nearest thousands, the population was __________.

Answer»

The population of Pune was 2,538,473 in 2001. Rounded off to nearest thousands, the population was 2,538,000.

235.

The expanded form of the number 9578 is (A) 9 × 10000 + 5 × 1000 + 7 × 10 + 8 × 1 (B) 9 × 1000 + 5 × 100 + 7 × 10 + 8 × 1 (C) 9 × 1000 + 57 × 10 + 8 × 1 (D) 9 × 100 + 5 × 100 + 7 × 10 + 8 × 1

Answer»

The correct option is (B) 9 × 1000 + 5 × 100 + 7 × 10 + 8 × 1.

Consider the given number 9578,

The place value of 8 is ones = 8 × 1

The place value of 7 is tens = 7 × 10

The place value of 5 is thousand = 5 × 100

The place value of 9 is ten thousand = 9 × 1000

236.

Numbers having more than two factors are called __________ numbers.

Answer»

Numbers having more than two factors are called Composite numbers.

237.

The number 58963 rounded off to nearest hundred is 58900.

Answer»

False

Given : Number 58963 rounded off to nearest hundred is 58900. 

To find : Is it true or false ? 

Solution : Rounded off to nearest hundred, 

1) If tens number is greater than or equal to 5 then hundredth place increased by one and rest became zero. 

2) If tens number is less than 5 then hundredth place remain same and rest became zero. 

In the number 58963, At tens place value is 6 > 5. 

So, the number became 59000. 

Therefore, it is false. 

238.

When rounded off to nearest thousands, the number 85642 is (A) 85600 (B) 85700 (C) 85000 (D) 86000

Answer»

The correct option is (D) 86000.

When rounded off to nearest thousands, the number 85642 is 86000

239.

The number 58963 rounded off to nearest hundred is 58900.

Answer»

The number 58963 rounded off to nearest hundred is 58900 is False.

240.

When rounded off to nearest thousands, the number 85642 is (A) 85600 (B) 85700 (C) 85000 (D) 86000

Answer» The correct option is (D) 86000.
241.

State whether the given statements are true (T) or false (F).Estimated sum of 7826 and 12469 rounded off to hundreds is 20,000.

Answer»

Estimated sum of 7826 and 12469 rounded off to hundreds is 20,000.

True

242.

State whether the given statement are true (T) or false (F).The numbers 4578, 4587, 5478, 5487 are in descending order.

Answer»

False.

In the question, the arrangement of the numbers in ascending order.

Descending order of the given number = 5487, 5478, 4587, 4578.

243.

Collect ‘5’ mobile numbers and arrange them in ascending and descending order.

Answer»

Let the 5 mobile numbers are: 

9247568320, 9849197602, 8125646682, 6305481954, 7702177046

Ascending order: 6305481954, 7702177046, 8125646682, 9247568320, 9849197602 

Descending older: 9849197602, 9247568320, 8125646682, 7702177046, 6305481954

244.

Write the given numbers in ascending and descending order.S.No.NumbersDescending order1.75645,77845,24625,856902.6790,27895,16176,50000S.No.NumbersAscending order1.75645,77845,24625,856902.6790,27895,16176,50000

Answer»
S.No.NumbersDescending order
1.75645,
77845,
24625,
85690
85690,
77845,
75645,
24625
2.6790,
27895,
16176,
50000
50000,
27895,
16176,
679

S.No.NumbersAscending order
1.75645,
77845,
24625,
85690
24625,
75645,
77845,
85690
2.6790,
27895,
16176,
50000
6790,
16176,
27895,
50000
245.

Compare the numbers written in the following table by writing them in ascending order:54329722310629352237912318263454344782

Answer»

The given number in ascending order are as :

54344782 > 243182634 > 23106293 > 5432972> 5223791

54344782
23182634
23106293
5432972
5223791

246.

By making a suitable chart, compare:(i) 540276 and 369998(ii) 6983245 and 6893254

Answer»

(i) 540276 and 369998

540276
369998

Clearly, both the numbers have equal number of digits i.e. 6

And at the leftmost, the first number has 5 and the second number has 3.

Since 5 > 3

540276 is greater.

(ii) 6983245 and 6893254

6983245
6893254

Clearly, both the numbers have equal number of digits i.e. 7

And at the leftmost, both have the same digit i.e. 6

And at the second place from the left, the first number has 9 and the second number has 8.

Since 9 > 8

6983245 is greater.

247.

Find five rational numbers between 1 and 2.

Answer»

We know, one rational number between two numbers m and n = (m+n)/2

Step 1: Rational number between 1 and 2 = (1+2)/2 = 3/2 

Step 2: Rational number between 1 and 3/2 = (1+3/2)/2 = 5/4 

Step 3: Rational number between 1 and 5/4 = (1+5/4)/2 = 9/8 

Step 4: Rational number between 3/2 and 2 = 1/2 [(3/2) + 2)] = 7/4 

Step 5: Rational number between 7/4 and 2 = 1/2 [7/4 + 2] = 15/8 

Arrange all the results: 1 < 9/8 < 5/4 < 3/2 < 7/4 < 15/8 < 2 

Therefore required integers are, 9/8, 5/4, 3/2, 7/4, 15/8.

248.

Find five rational numbers between 3/5 and 4/5.

Answer»

Steps to find n rational numbers between any two numbers: 

Step 1: Multiply and divide both the numbers by n + 1. 

In this example, we have to find 5 rational numbers between 3/5 and 4/5. Here n = 5 

Multiply 3/5 and 4/5 by 6 

3/5 x 6/6 = 18/30 and 

4/5 x 6/6 = 24/30 

Step 2: Choose 5 numbers between 18/30 and 24/30 

3/5 = 18/30 < 19/30 < 20/30 < 21/30 < 22/30 < 23/30 < 24/30 = 4/5 

Therefore, 5 rational numbers between 3/5 and 4/5 are 19/30, 20/30, 21/30, 22/30, 23/30.

249.

Are the following statements true or false? Give reason for your answer.  (i) Every whole number is a natural number.(ii) Every integer is a rational number.(iii) Every rational number is an integer.(iv) Every natural number is a whole number,(v) Every integer is a whole number.(vi) Every rational number is a whole number.

Answer»

(i) False. As 0 is not a natural number.

(ii) True.

(iii) False. Numbers such as 1/2, 3/2, 5/3 are rational numbers but not integers.

(iv) True.

(v) False. Negative numbers are not whole numbers.

(vi) False. Proper fractions are not whole numbers

250.

Write the following in expanded form. i) 756723 ii) 60567234 iii) 8500756762

Answer»

i) 756723 

Expanded form: 7 × 1,00,000 + 5 × 10,000 + 6 × 1,000 + 7 × 100 + 2 × 10 + 3 × 1 

: 7 lakhs + 5 ten thousands + 6 thousands + 7 hundreds + 2 tens + 3 ones 

Word form: Seven lakh fifty six thousand seven hundred and twenty three.

ii) 60567234 

Expanded form: 6 × 1,00,00,000 + 5 × 1,00,000 + 6 × 10,000 + 7 × 1,000 + 2 × 100 + 3 × 10 + 4 × 1 

: 6 crores + 5 lakhs + 6 ten thousands + 7 thousands + 2 hundreds + 3 tens + 4 ones 

Word form: Six crore five lakh sixty seven thousand two hundred and thirty four.

iii) 8500756762 

Expanded form: 8 × 1,00,00,00,000 + 5 × 10,00,00,000 + 7 × 1,00,000 + 5 × 10,000 + 6 × 1000 + 7 × 100 + 6 × 10 + 2 × 1 

: 8 hundred crores + 5 ten crores + 7 lakhs & 5 ten thousands + 6 thousands + 7 hundreds + 6 tens + 2 ones 

Word form: Eight hundred and fifty crore seven lakh fifty six thousand seven hundred and sixty two.