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51.

Mean of 100 observations is 40. The 9th observation is 30. If this is replaced by 70 keeping all other observations same, find the new mean. (A) 40.6 (B) 40.4 (C) 40.3 (D) 40.7

Answer»

(B) 40.4

New mean = (4000 − 30 + 70)/100

= 40.4

52.

If the number of scores is odd, then the ( \(\frac{n+1}{2}\)) score is the median of the data. That is, the number of scores below as well as above K\(\frac{n+1}{2}\) is \(\frac{n- 1}{2}\) Verify the fact by taking n = 2m + I.

Answer»

proof:

Given that, n = 2m + 1

∴ The sequence of the terms of scores can be 1, 2, 3, ...., 2m + 1

Here,  (n +1)/2 = (2m + 1 + 1)/2 

= (2m + 2)/2 = 2(m + 1)/2 

= m + 1

The sequence of the terms of scores is 

1,2, 3, …….., m, m + 1, m + 2, …, 2m + 1 

Thus, we have to prove that m + 1 is the middle term if the number of scores is 2m + 1 

i.e. to prove 

number of terms from 1 to m = number of terms from m + 2 to 2m + 1 …(i) 

Consider the L.H.S. of equation (i) 

The sequence is an A.P. with a = 1,d = 1,

tn1 = m 

tn1 = a + (n1 – 1) d 

∴ m = 1 + (n1 – 1)1 

∴ m = 1 + n1 – 1 

∴ m = n1 

Consider the R.H.S. of equation (ii)

The sequence is an A.P. with a = m + 2, d = 1, tn2 = 2m + 1 

tn2 = a + (n2 – 1)d 

∴ 2m + 1 = m + 2 + (n2 – 1)1 

∴ 2m + 1 = m + n2 + 1 

∴ m = n2 

∴ number of terms from 1 to m = number of terms from m + 2 to 2m + 1 = m = (n-1)/2

∴ m + 1 is the middle term if the number of scores is 2m + 1.

53.

In a basket there are 10 tomatoes. The weight of each of these tomatoes in grams is as follows: 60, 70, 90, 95, 50, 65, 70, 80, 85, 95.Find the median of the weights of tomatoes.

Answer»

Given data in ascending order: 

50, 60, 65, 70, 70, 80 85, 90, 95, 95 

∴ Number of observations (n) = 10 (i.e., even) 

∴ Median is the average of middle two observations 

Here, 5th and 6th numbers are in the middle position 

∴ Median = (70 + 80)/2

∴ Median = 150/2

∴ The median of the weights of tomatoes is 75 grams.

54.

Distance covered per litre (km)12-1414-1616-1818-20No. of cars1112207The median of the distances covered per litre shown in the above data is in the group(A) 12 – 14 (B) 14 – 16 (C) 16 – 18 (D) 18 – 20

Answer»

The correct answer is : (C) 16 – 18 

55.

The average weight of 5 packets is 24 kgs and the average weight of another 10 packets is 12 kgs, then average weight of 15 packets is ………………. A) 6 Kgs B) 16 Kgs C) 10 Kgs D) 36 Kgs

Answer»

Correct option is (B) 16 Kgs

Average weight of 15 packets \(=\frac{5\times24+10\times12}{15}\)

\(=\frac{120+120}{15}\)

\(=\frac{240}{15}\) = 16 kg

Correct option is  B) 16 Kgs

56.

No. of tress plants by each student 1-34-67-910-12No. of Students7864The above is to be shown by a frequency polygon. The coordinated of the points to show number of student in the class 4 - 6 are.(A) (4, 8) (B) (3,5) (C) (5,8) (D) (8,4)

Answer»

 (C) (5,8)

Class mark = 5 

Frequency = 8 

∴ Co-ordinates of the point = (5, 8)

57.

Observe the following frequency polygon and write the answers of the questions below it.i. Which class has the maximum number of students? ii. Write the classes having zero frequency. iii. What is the class mark of the class, having frequency of 50 students? iv. Write the lower and upper class limits of the class whose class mark is 85. v. How many students are in the class 80 – 90?

Answer»

i. The class 60 – 70 has the maximum number of students. 

ii. The classes 20 – 30 and 90 – 100 have frequency zero. 

iii. The class mark of the class having 50 students is 55. 

iv. The lower and upper class limits of the class having class mark 85 are 80 and 90 respectively

v. There are 15 students in the class 80 – 90.

58.

What is the Range of the following data , 7, -100,3,8,4,13,4,7,3,100,11,7,0 ?A. 200B. 0C. 100D. -100

Answer» Correct Answer - A
59.

Choose the correct alternative among the following : The class mark of the class interval 120-130 is,A. 120B. 130C. 122.5D. 125

Answer» Correct Answer - A
60.

The class mark of the class 100-130 is:A. 100B. 15C. 105D. 115

Answer» Correct Answer - D
61.

What is the Range of the following data ,13 ,7,23,8,4,103,4,7,3,10,11,7,0 ?A. 103B. 100C. 93D. 73

Answer» Correct Answer - A
62.

In a frequency distribution, the mid value of a class is 10 and the lower class of the class is 4. The upper limit of the class is:A. 12B. 10C. 8D. 16

Answer» Correct Answer - D
63.

A survey was conducted by a group of students as a part of their environment awareness programme, in which they collected the following data regarding the number of plants in 20 houses in a locality. Find the mean number of plants per house.Which method did you use for finding the mean, and why?

Answer» `x_i = 1,3,5,7,9,11,13`
`f_i = 1,2,1,5,6,2,3`
`f_ix_i= 1, 6,5,35,54,22,39`
`sum f_i = 20`
`sum f_ix_i= 162`
mean`= (sum f_ix_i)/(sum f_i)`
`=162/20=8.1`
answer
64.

Theaverage marks of boys in a class is 52 and that of girls is 42. The averagemarks of boys and girls combined is 50. The percentage of boys in the classis(1)40(2) 20(3) 80(4) 60A. 40B. 20C. 80D. 60

Answer» Correct Answer - C
52x+42y=50(x+y)
`implies 2x=8y`
`implies (x)/(y)=(4)/(1) " and" (x)/(x+y)=(4)/(5)`
The percentage of boys is 80.
65.

The upper class limit of inclusive type class interval 10-20 is ______.A. 10.5B. 20C. 20.5D. 17.5

Answer» Correct Answer - B
For inclusive type class, given values are the limits.
66.

In a frequency distribution, the mid value of a class is 30 and the lower class of the class is 10. The upper limit of the class is:A. 50B. 10C. 20D. 15

Answer» Correct Answer - A
67.

If Y be the mid point and 2 is the upper class limit in a continuous frequency distribution .What is the lower class limit?A. 2Y-1B. 2(Y-1)C. Y-2D. Y-1

Answer» Correct Answer - A
68.

Classify following information as primary or secondary data.i. In the village Nandpur, the information collected from every house regarding students not attending school. ii. For science project, information of trees gathered by visiting a forest

Answer»

i. Primary data 

ii. Primary data

69.

For the above given activity, the information of number of girls per 1000 boys is given for five states. The literacy percentage of these five states is given below. Assam (73%), Bihar (64%), Punjab (77%), Kerala (94%), Maharashtra (83%). Think of the number of girls and the literacy percentages in the respective states. Can you draw any conclusions from it?

Answer»

By observing the number of girls per 1000 boys and literacy percentages in the given respective states, we can conclude that the literacy rate of girls is least in Bihar and is highest in Kerala.

70.

For class interval 20 – 25 write the lower class limit and the upper class limit.

Answer»

Lower class limit = 20 

Upper class limit = 25

71.

Classify following information as primary or secondary data. i. Information of attendance of every student collected by visiting every class in a school ii. The information of heights of students was gathered from school records and sent to the head office, as it was to be sent urgently. iii. In the village Nandpur, the information collected from every house regarding students not attending school. iv. For science project, information of trees gathered by visiting a forest.

Answer»

i. Primary data 

ii. Secondary data 

iii. Primary data 

iv. Primary data

72.

Classify following information as primary or secondary data.i. Information of attendance of every student collected by visiting every class in a school ii. The information of heights of students was gathered from school records and sent to the head office, as it was to be sent urgently

Answer»

i. Primary data 

ii. Secondary data

73.

The line graph shows the attendance of 35 students over a week. (i) On which day of the week was more number of student present ? (ii) If 18 boys were present on Thursday, then how many girls were present on the same day ?

Answer» Correct Answer - (i) Monday (ii) 12
(i) Monday
(ii) The number of students present on Thursday = 30
The number of boys present on Thursday = 18
`:.` the number of girls present on Thursday =30-18=12.
74.

A class teacher has the following absentee record of 40 students of a class for the whole term. Find the mean number of days a student was absent.

Answer» We can find the mean using step deviation method.
First, we have to construct a table with given details.
Please refer to video for constructing the complete table.
So, Mean`(barX) = A+(sumf_iU_i)/(sumf_i)**h`
As per the constructed table,
`A = 17,sumf_iU_i = -90.5,sumf_i = 40 and h = 2`
So,Mean`(barX) = 17+(-90.5/40**2)`
`barX = 17-4.525 = 12.475`
75.

Find the mode of the following distribution of marks obtained by 80students:Marks obtained   0-10         10-20                           20-30       30-40                           40-50No. of students   6              10                           12            32                           20

Answer» In this question, Modal class is 30-40. So, `l` is 30.
Frequency of Modal class`(f) `= 32
Frequency of Pre Modal class`(f1)` = 12
Frequency of succeeding Modal class`(f2)` = 20
Interval`(i)` = 10
We know, Mode = `l+((f-f1)/(2f-f1-f2))**i`
Putting tthe above values in formula,
Mode = `30+((32-12)/(2**32-12-20))*10`
= `30+(20**10/32)`
`Mode = 36.25`
76.

Thirty women were examined in a hospital by a doctor and the number of heart beats per minute recorded and summarized as follows. Find the mean heart beats per minute for these women, choosing a suitable method. Number of heart beats per minute:65 - 6868 - 7171 - 7474 - 7777 - 8080 - 8383 - 86 Number of women:2438742

Answer»

We may find class mark of each interval (xi) by using the relation.

xi \(=\frac{Upper\,class\,limit+Lower\,class\, limit}{2}\)

Class size of this data = 3

Now taking 75.5 as assumed mean (A), we may calculate di, ui, fiui as following:

 No. of heart beat per minute  Number of women (fi) xi di = xi - 75.5 ui\(\frac{xi-75.5}{h}\) fiui
 65 - 68 2 66.5-9-3-6
 68 - 71 4 69.5-6-2-8
 71 - 74 3 72.5-3-1-3
 74 - 77 8 75.5000
 77 - 80 7 78.5 317
 80 - 83 4 81.5 628
 83 - 86 2 84.5 9 3 6
 N = 30\(\sum\)fiui = 4

Now we may observe from table that ∑fi = 30, ∑fiui = 4

Mean (X̅) = di + \(\frac{\sum f_ iu_i }{\sum f_i}\times h\)

\(=75.5\,+\frac{4}{30}\times3\)

\(=75.5 \,+0.4 = 75.9\) 

77.

Define qualitative characteristics with example.

Answer»

The demand for accounting information by investors, lenders, creditors, etc., creates fundamental qualitative characteristics that are desirable in accounting information. There are six qualitative characteristics of accounting information. Two of the six qualitative characteristics are fundamental (must have), while the remaining four qualitative characteristics are enhancing.

The qualitative characteristics of accounting information are as follows:-

  1. Reliability-The first qualitative characteristic of accounting information is reliability. Reliability means the users must be able to depend on the information. It is believed that reliable information should be free from error and bias and faithfully represents what it is meant to represent.
  2. Relevance-The second qualitative characteristic of accounting information is relevance. It is believed that relevant, information must be available in time, must help in prediction and feedback and must influence the decisions of users in a positive manner.
  3. Understandability- Understandability is the third most important qualitative characteristic of accounting information. Understandability means decision-makers must interpret accounting information in the same sense as it is prepared and conveyed to them.
  4. Comparability-The last qualitative characteristic of accounting information is comparability. It is believed that it is not sufficient that the financial information is relevant and reliable at a particular time, in a particular circumstance or for a particular reporting entity. 
78.

The following table gives the number of boys of a particular age in a class of 40 students. Calculate the mean age of the students.Age (in year):151617181920No. of students:38101054

Answer»
Age (x)No. of students (y)yx
15345
168128
1710170
1810180
19595
20480
N = 40\(\sum\)yx = 698

Mean = \(\frac{\sum yx}{N}\)

\(=\frac{698}{40}=17.45\)

Therefore, 

mean age is 17.45 years.

79.

The temperatures of a city recorded during a week are 42°, 35°, 44°, 33°, 39°, 45° and 42°. The average temperature is A) 42° B) 35° C) 39° D) 40°

Answer»

Correct option is (D) 40°

Average temperature \(=\frac{\text{Sum of temperatures in a week}}7\)

\(=\frac{42^\circ+35^\circ+44^\circ+33^\circ+39^\circ+45^\circ+42^\circ}7\)

\(=\frac{280^\circ}7=40^\circ\)

Correct option is  D) 40°

80.

The wickets taken by a bowler in 10 cricket matches are as follows:2          6          4          5          0          2          1          3            2          3Find the mode of the data.

Answer» Please refer to the frequency distribution table created in video.
As per table,we can see that
Number of matches are maximum when the bowler has taken `2` wickets.So, mode of the given data is `2`.
81.

Find the mean of the marks obtained by 30 students of Class IX of aschool, given in Example 2.10 20 36 92 95 40 50 56 60 7092 88 80 70 72 70 36 40 36 4092 40 50 50 56 60 70 60 60 88

Answer» We know,
`Mean = `Sum of all observations`/`Total number of observations
Here, Sum of all observations ` = 10 + 20+ 36+ 92+ 95 +40`
`+ 50+ 56+ 60+ 70+92+ 88+ 80 +70+ 72+ 70`
`+36+ 40+ 36 +40+92+ 40+ 50+ 50+ 56+ 60+ 70 +60+ 60+ 88= 1779`
Total number of observations `=30`
So, `Mean = 1779/30 = 59.3`
82.

Find the class marks of classes 10 - 25 and 35 - 55

Answer»

We know, 

class marks of a class interval is

\(=\frac{1}{2}(lower\,limit+upper\,limit)\)

For 10 - 25 

Lower limit = 10 

Upper limit = 25

Class mark = \(\frac{1}{2}(10+25)=17.5\)

For 35 - 55 

Lower limit = 35 

Upper limit = 55

Class mark = \(\frac{1}{2}(35+55)=45\)

83.

If the class intervals in a frequency distribution are (72 - 73.9), (74 - 75.9), (76 - 77.9), (78 - 79.9) etc., the midpoint of the class (74 - 75.9) is(A) 74.50 (B) 74.90 (C) 74.95 (D) 75.00

Answer» (C) The midpoint of the class (74 - 75.9) is 74.95.
84.

There are 20 students in a class of them, the height of ten students is 150 cm each, the height of 6 students is 142 cm each and the height of 4 students is 132 cm each. Find the average height of all the students.A. 144B. 140C. 138D. 146

Answer» Correct Answer - A
The average height `=(10xx150+6xx142+4xx132)/20`
`=(1500+852+528)/20=2880/20=144`
Hence, the correct option is (a).
85.

If the mean height of 3 boys is 142 cm. and the mean height of another 7 students is 145 cm., then the mean height of 10 students.A) 144 cm B) 144.1 cm C) 144.2 cm D) 144.4 cm

Answer»

Correct option is (B) 144.1 cm

The mean height of 10 boys \(=\frac{3\times142+7\times145}{10}\)

\(=\frac{426+1015}{10}\)

\(=\frac{1441}{10}\) = 144.1 cm

Correct option is  B) 144.1 cm

86.

If the heights of five students in a class are 132 cm, 158 cm, 150 cm, 145 cm, and 155 cm, then find their mean height.

Answer» Correct Answer - 148 cm
87.

Find the mean deviation (approximately) about the mean for the following. `{:("Class interval",f),(" "0-5,3),(" "5-0,4),(" "10-15,8),(" "15-20,10),(" "20-25,5):}`A. 5B. 4C. 6D. 3

Answer» Correct Answer - A
(i) Find mean and then mean deviation.
(ii) Find the mid-values of the series.
(iii) Find the mean.
(iv) Find the mean deviation using the formula, `MD = sqrt((sum(x_(i)-A)f)/(sum f))`
88.

The mean height of 25 boys in a class is 150 cm , and the mean height of 35 girls in the same class is 145 cm . The combined mean height of 60 students in the class is `"_______"` (approximately).A. 143 cmB. 146 cmC. 147 cmD. 145 cm

Answer» Correct Answer - c
Given `n_(1) = 25 , n_(2) = 35`
`barx_(1) = 150` and `barx_(2) = 145`
Combined mean , `barx = (n_(1) barx_(1) + n_(2)barx_(2))/(n_(1) + n_(2))`
`barx = (25 xx 150 + 35 xx 145)/(25 + 35) = (3750 + 5075)/(60)`
`= (8825)/(60) = 147` (approximately ) .
89.

If the average mark of 15 students is 60 and the average mark of another 10 students is 70, then find the average mark of 25 students. The following are the steps involved in solving the above problem. Arrange them in sequential order. (A) Average marks of 25 students `= (1600)/(25) = 64` (B) The total marks of 15 students `= 15 xx 60 = 900` The total marks of 10 students `= 10 xx 70 = 700` (C) The total marks of 25 students = 900 + 700 = 1600A. BCAB. BACC. CBAD. CAB

Answer» Correct Answer - A
BCA is the required sequential order.
90.

In a class of 25 boys and 20 girls, the mean weight of the boys is 40 kg and the mean weight of the girls is 35 kg. Find the mean weight of the class. The following are the steps involved in solving the above problem. Arrange them in sequential order. (A) The total weight of 25 boys `= 25 xx 40 = 1000` kg The total weight of 20 girls `=20 xx 35 = 700` kg (B) The mean weight of the class `= (1700)/(45) = 37(7)/(9)`kg (C) The total weight of 45 students = 1000 kg + 700 kg = 1700 kgA. ABCB. ACBC. BCAD. CBA

Answer» Correct Answer - B
ACB is the required sequential order.
91.

If `p lt q lt 2p`, the median and mean of p, q and 2p are 36 and 31 respectively, then find the mean of p and q.A. 21.5B. 23C. 27.5D. 24

Answer» Correct Answer - C
as p, q and 2p are in descending order, their median is 36.
`therefore q = 36`
`(p +q + 2p)/(3) = 31`
`rArr 3p + 36 = 93 rArr p = 19`.
`therefore "Mean of 19 and 36" = (19 + 36)/(2) = 27.5`.
92.

The variance of `6x_(i) + 3` is 30 , find the standard deviation of `x_(i)` .A. `(5)/(sqrt6)`B. `sqrt((5)/(6))`C. `30`D. `sqrt(30)`

Answer» Correct Answer - b
(i) If the variance of `(ax_(i) +b)` is k , then SD of `(ax_(i) + b) = sqrtk`.
(ii) SD of `x_(i) = (sqrtk)/(a)`.
93.

If ` a lt b lt c lt d ` and a , b , c , d are non-zero integers , the mean and median of a , b , c , d is 0 , then which of the following is correct ?A. `b = -c `B. `a = -d `C. Both (a) and (b)D. None of these

Answer» Correct Answer - c
Average = `("Sum of the quantities")/("Number of the quantities")`
94.

If `a lt b lt 2a` , and the mean and the median of a , b and 2a are 15 and 12 , then find a .A. 7B. 11C. 10D. 8

Answer» Correct Answer - b
(i) Since , ` a lt b lt 2a` ,Median = b= 12 .
(ii) Mean = `("Sum of all observations")/("Total number of observations")`.
95.

If L = 44.5 , N = 50 , F = 15 , f = 5 and C = 20 , then find the median from of given data .A. 84.5B. 74.5C. 64.5D. 54.5

Answer» Correct Answer - a
Median = `L + [(((N)/(2) - F) C)/(f)]`
96.

If L = 39.5 , `Delta_(1) = 6 , Delta_(2) = 9` and c = 10 , then find the mode of the data .A. 45.5B. 43.5C. 46.5D. 44.5

Answer» Correct Answer - b
Mode = `L_(1) + [((f-f_(1))C)/(2f- (f_(1) - f_(2)))]` .
97.

A data has 13 observations arranged in descending order. Which observation presents the median of the data ?A) 17th B) 6th C) 7th D) None

Answer»

Correct option is: C) 7th

\(\because\) n = Number of observations = 13 which is odd

\(\therefore\) \(\frac {n+1}{2} = \frac {13+1}{2} = \frac {14}2 = 7^{th}\) observation is median of the given data.

Hence, \(7^{th}\) observation arranged in ascending or descending order is median of the data.

Correct option is: C) 7th

98.

The average weight of 55 students is 55 kg , and the average weight of another 45 students is 45 kg . Find the average weight of all the students .A. 48 kgB. 50 kgC. 50.5 kgD. 52.25 kg

Answer» Correct Answer - c
Average = `("Sum of the quantities")/("Number of the quantities")`
99.

The mean of 10 observations is 15.5 . By an error , one observation is registered as 13 instead of 34. Find the actual mean .

Answer» Correct Answer - 17.6
100.

The mean of 20 observations is 12.5. By error, one observation was noted as -15 instead of 15. Then the correct mean is ....(A) 11.75(B) 11(C) 14 (D) 13

Answer»

The correct option is: (C) 14 

Explanation:

The incorrect sum of observations = 12.5 x 20 = 250

Now, correct sum = 250 - (-15) + 15 = 280

.'. Correct mean = 280/20 = 14