# Statistics – Class 9 /Maths.

**Chapter 14 of NCERT/CBSE Class 9 Maths is about Statistics. Herein this lesson you can find out practice problems for this chapter.**

**CBSE CLASS 9 MATHEMATICSStatistics – Chapter 14 / Sample paper.Fill in the blanks:**

- Facts or figures collected with a definite purpose are called ————
- The area of study dealing with the presentation, analysis and interpretation of data is ————–
- Which is the most frequently occurring observation?
- The class mark of the class 20-30 is ———–
- The range of the data 25, 23, 20, 29, 38, 40, 45, 50 is —————-
**Answer the following:** - Find the mean of first 10 prime numbers?
- If the mean of the following observations x, x-2, x-4, x-5, x+11 is 10, then find the value of x?
- Arithmetic mean of terms 55, 52, 59, x, 60 is 50. Find the value of x?
- Find the median of first five prime numbers?
- Find the mode of the following marks (out of 10) obtained by 20 students:

4,6,5,9,3,2,7,7,6,5,4,9,10,10,3,4,7,6,9,9. - The following observations have been arranged in ascending order. If the median of the data is 63, find the value of x?

29, 32, 48, 50, x, x + 2, 72, 78, 84, 95. - The following number of goals was scored by a team in a series of 10 matches: 2, 3, 4, 5, 0, 1, 3, 3, 3, 4, 3. Find the mean, median and mode of the scores?
- Find the mean of first 5 multiples of 5?
- The mean of x and y is 10 and Mean of x, y and z is 15. Find the value of z?
- Find the mode of 14, 25, 14, 28, 18, 17, 18, 14, 23, 22, 14, 18.

**ANSWERS:**

- Data
- Statistics
- Mode
- 25

5.30 - Mean = Sum of all observations/ Total number of observations

= 2+3+5+7+11+13+17+19+23+29/10

= 129/10

= 12.9 - Given mean = 10

x + x -2 + x – 4 + x – 5 + x+ 11/5 = 10

5x/5 = 10

x = 10. - Given mean = 50

55 + 52 + 59 + x + 60 /5 = 50

226 + x = 250

x = 250 – 226 = 24 - First 5 prime numbers are 2, 3, 5, 7 and 11.These numbers are in ascending order. So median = 5
- Here 9 occurs most frequently, i.e., 4 times.

So the mode is 9. - Given Median = 63

So (x + x + 2)/2 = 63

2x + 2 = 126

2x = 126 – 2 = 124

x = 124/2 = 62. - Mean = 2 + 3 + 4+ 5 + 0 + 1+ 3 + 3 + 4 + 3/10

= 28/10 = 2.8.

Mode = 3 (occurs 4 times)

To find Median, arrange the numbers in ascending order:

0, 1, 2, 3, 3, 3, 3, 4, 4, 5

Median = (3 + 3)/2 = 6/2 = 3 - Multiples of 5 are 5, 10, 15, 20, and 25.

Mean = (5 + 10 + 15 + 20 + 25)/5 = 75/5 = 15. - Given (x + y) /2= 10

x + y = 20

Also (x + y + z)/3= 15

x + y + z = 45

20 + z = 45

z = 45 – 20 = 25. - Mode = 14, because 14 occurs 4 times.