Finding Mean for Grouped Data When Class Intervals Are Not Given

Q. If the mean of 6, 7, x, 8, y, 14 is 9, then

(a) x + y = 21
(b) x + y = 19
(c) x − y = 19
(d) x − y = 21

Q.

What is the full form of LAC?

Q.

The mean of the first 10 natural numbers is 55.

1. True

2. False

Q.

If the mean of the following distribution is 2.6, then the value of y is

1. 13

2. 24

3. 8

4. 3

Q.

Find the average height of students in a class from the given table:

$\begin{array}{cc}\text{Height in cm}& \text{Number of students}\\ 120& 5\\ 130& 6\\ 140& 9\\ 150& 10\\ 160& 4\\ 170& 2\end{array}$

1. 140

2. 142.22

3. 150

4. 152.22

Q. If the mean of the following distribution is 54, find the value of p:

Class :	0−20	20−40	40−60	60−80	80−100
Frequency :	7	p	10	9	13

Q. If the mean of the following frequency distribution is 24, find the value of p. [CBSE 2013]

Class	0−10	10−20	20−30	30−40	40−50
Frequency	3	4	p	3	2

Q. If the mean of the following distribution is 27, find the value of p.

Class	0−10	10−20	20−30	30−40	40−50
Frequency	8	p	12	13	10

Q.

The runs scored by two batsmen A and B in six innings are given as follows:

Batsman A	48	50	54	46	48	54
Batsman B	46	44	43	46	45	46

Determine (i) Who is a better run getter? (ii) Who is a consistent player?

Q. ​The weights of tea in 70 packets are shown in the following table:

Weight (in grams)	200−201	201−202	202−203	203−204	204−205	205−206
Number of packets	13	27	18	10	1	1

Find the mean weight of packets using step-deviation method. [CBSE 2013]

Q.

Calculate the mean for the following distribution:
x : 5 6 7 8 9
f : 4 8 14 11 3

Q.

The mean of 20 numbers is zero.Of them, at the most, how many may be greater than zero?

(a) 0 (b) 1 (c) 10 (d) 19

Q. The mean of 1, 3, 4, 5, 7, 4 is m. The numbers 3, 2, 2, 4, 3, 3, p have mean m − 1 and median q. Then, p + q =

(a) 4
(b) 5
(c) 6
(d) 7

Q. The mean of the following data is 42, find the missing frequencies x and y if the sum of the frequencies is 100.

Class interval	0−10	10−20	20−30	30−40	40−50	50−60	60−70	70−80
Frequency	7	10	x	13	y	10	14	9

Q. The number of students absent in a class were recorded every day for 120 days and the information is given in the following frequency table:

No. of students absent (x):	0	1	2	3	4	5	6	7
No. of days (f):	1	4	10	50	34	15	4	2

Find the mean number of students absent per day.

Q. The mean of the following distribution is 54, find the missing frequency x

CI	0-20	20-40	40-60	60-80	80-100
F	16	14	24	26	x

Q. If the mean of first n natural numbers is $\frac{5n}{9}$, then n =

(a) 5
(b) 4
(c) 9
(d) 10

Q. The following table shows the marks scored by 140 students in an examination of a certain paper.

Marks:	0−10	10−20	20−30	30−40	40−50
Number of students:	20	24	40	36	20

Calculate the average marks by using all the three methods: direct method, assumed mean deviation and shortcut method.

Q.

The average weight of a group of 25 men was calculated to be 78.4 kg. It was discovered later that one weight was wrongly entered as 69 kg instead of 96 kg. What is the correct average ?

1. 79.48

2. 77.56

3. 80.30

4. 75.76

Q. The mean of first n odd natural numbers is $\frac{n^2}{81}$, then n =
(a) 9
(b) 81
(c) 27
(d) 18

Q.

The observations 29, 32, 48, 50, x, x+2, 72, 78, 84, 95 are arranged in ascending order.What is the value of x if the median of the data is 63?

Q.

Question 93

The time taken by Rohan in five different races to run a distance of 500 m was 3.20 minutes, 3.37 minutes, 3.29 minutes 3.17 minutes and 3.32 minutes find the average times taken by him in the races.

Q.

the mean of 2, 7, 6 and x is 15 and the mean of 18, 1, 6, x and y is 10.What is the value of y?

(a)5 (b)10 (c)20 (d)30

Q. The mean of 10 numbers is 12.5. The mean of first six numbers is 15 and the mean of last five terms is 10. Find the sixth number l.

Q.

The distributions X and Y with total number of observations 36 and 64, and mean 4 and 3 respectively are combined.What is the mean of the resulting distribution X+Y?

Q.

The mean of 15 numbers is 25. If each number is multiplied by 4, mean of the new numbers is

1. 40

2. 60

3. 100

4. 10

Q. If the mean of numbers 28, x, 42, 78 and 104 is 62, what is the mean of 48, 62, 98, 124 and x?

1. 58
2. 78
3. 390
4. 310

Q. If the mean of the number $27+x,31+x,89+x,107+x,156+x$ is $82,$ then the mean of $130+x,126+x,68+x,50+x,1+x$ is ___.

Q.

The mean of the marks obtained by 7 students in a group is 226. If the marks obtained by six of them are 340, 180, 260, 56, 275, 307, then the marks obtained by the seventh student are

1. 125

2. 174

3. 164

4. 200

Q.

The average weight of a class having 100 students is 40 kg. The number of boys in the class is 60 and the number of girls is 40. The average weight of boys is 45. Find the average weight of girls.

1. 34 kg

2. 33 kg

3. 32.5 kg

4. 30 kg