## Chapter 7 Statistics R.D. Sharma Solutions for Class 10th Math Exercise 7.2

1. The number of telephone calls received at an exchange per interval for 250 successive one- minute intervals are given in the following frequency table:
No. of calls(x): 0 1 2 3 4 5 6

No. of intervals (f): 15 24 29 46 54 43 39

Compute the mean number of calls per interval.Â Â

No. of intervals (f): 15 24 29 46 54 43 39

Compute the mean number of calls per interval.Â Â

**SolutionÂ**

2. Five coins were simultaneously tossed 1000 times, and at each toss the number of heads was observed. The number of tosses during which 0,1,2,3,4 and 5 heads were obtained are shown in the table below. Find the mean number of heads per toss

No. of heads per toss (x): 0Â Â Â 1Â Â 2Â Â 3Â Â Â 4Â Â Â 5

No. of tosses (f):Â Â Â Â Â Â Â 38 144 342 287 164 25

No. of heads per toss (x): 0Â Â Â 1Â Â 2Â Â 3Â Â Â 4Â Â Â 5

No. of tosses (f):Â Â Â Â Â Â Â 38 144 342 287 164 25

**Solution**

3. The following table gives the number of branches and number of plants in the garden of a

school.

No. of branches (x): 2Â Â 3Â Â 4Â Â 5Â Â 6

No. of plantsÂ Â Â (f): 49 43 57 38 13

Calculate the average number of branches per plant.Â

school.

No. of branches (x): 2Â Â 3Â Â 4Â Â 5Â Â 6

No. of plantsÂ Â Â (f): 49 43 57 38 13

Calculate the average number of branches per plant.Â

**SolutionÂ**

4. The following table gives the number of children of 150 families in a village

No. of children (x): 0 1 2 3 4 5

No. of families (f): 10 21 55 42 15 7

Find the average number of children per family.

No. of children (x): 0 1 2 3 4 5

No. of families (f): 10 21 55 42 15 7

Find the average number of children per family.

**SolutionÂ**

5. The marks obtained out of 50, by 102 students in a Physics test are given in the frequency

table below:

Marks(x):Â Â Â Â 15 20 22 24 25 30 33 38 45

Frequency (f): 5Â 8Â Â 11 20 23 18 13Â 3Â 1Â

Find the average number of marks.Â

**SolutionÂ**Â

6. 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 1Â Â 2Â Â 3Â Â 4Â Â 5 6Â 7

No. of days (f):Â Â Â Â Â Â Â Â Â Â 1 4 10 50 34 15 4 2

Find the mean number of students absent per day.

No. of students absent (x): 0 1Â Â 2Â Â 3Â Â 4Â Â 5 6Â 7

No. of days (f):Â Â Â Â Â Â Â Â Â Â 1 4 10 50 34 15 4 2

Find the mean number of students absent per day.

**SolutionÂ**

7. In the first proof reading of a book containing 300 pages the following distribution of

misprints was obtained:

No. of misprints per page (x): 0Â Â Â 1Â Â Â 2Â Â 3Â Â 4Â Â 5

No. of pages (f):Â Â Â Â Â Â Â Â Â Â Â 154 95Â 36Â Â 9Â Â 5Â Â 1

Find the average number of misprints per page.Â Â

misprints was obtained:

No. of misprints per page (x): 0Â Â Â 1Â Â Â 2Â Â 3Â Â 4Â Â 5

No. of pages (f):Â Â Â Â Â Â Â Â Â Â Â 154 95Â 36Â Â 9Â Â 5Â Â 1

Find the average number of misprints per page.Â Â

**SolutionÂ**Â

8. The following distribution gives the number of accidents met by 160 workers in a factory

during a month.

No. of accidents (x): 0 1 2 3 4

No. of workers (f): 70 52 34 3 1

Find the average number of accidents per worker.

during a month.

No. of accidents (x): 0 1 2 3 4

No. of workers (f): 70 52 34 3 1

Find the average number of accidents per worker.

**SolutionÂ**Â

9. Find the mean from the following frequency distribution of marks at a test in statistics:

Marks(x): 5 10 15 20 25 30 35 40 45 50

No. of students (f): 15 50 80 76 72 45 39 9 8 6

Marks(x): 5 10 15 20 25 30 35 40 45 50

No. of students (f): 15 50 80 76 72 45 39 9 8 6

**SolutionÂ**