RS Aggarwal Class 7 Mathematics Twenty One Chapter Collection and Organisation of Data (Mean, Median and Mode) Exercise 21B Solution

RS Aggarwal Class 7 Mathematics Twenty One Chapter Collection and Organisation of Data (Mean, Median and Mode) Exercise 21B Solution

EXERCISE 21B

(1) Find the median of:

(i) 3, 11, 7, 2, 5, 9, 9, 2, 10

Solution: Arranging the numbers in ascending orders,

2, 2, 3, 5, 7, 9, 9, 10, 11

Number of terms, n = 9; it is an odd number.

Median = (9+1)/2 th observation

Median = 5th observation.

Median = 7.

(ii) 9, 25, 18, 15, 6, 16, 8, 22, 21

Solution: Arranging the number in ascending orders

6, 8, 9, 15, 16, 18, 21, 22, 25

Number of terms, n = 9; it is an odd number.

Median = (9+1)/2 th observation

Median = 5^th observation

Median = 16

(iii) 21, 15, 6, 25, 18, 13, 20, 9, 16, 8, 22

Solution: Arranging the numbers in ascending order,

6, 8, 9, 13, 15, 16, 18, 20, 21, 22, 25

Number of terms, n = 11; it is an odd number.

Median = (11+1)/2 th observation

Median = 6th observation

Median = 16

(2) Find the median of:

(i) 10, 32, 17, 19, 21, 22, 9, 35

(ii) 55, 60, 35, 51, 29, 63, 72, 91, 85, 82

(3) Find the median of first 15 odd numbers.

(4) Find the median of first 10 even numbers.

(5) Find the median of first 50 whole numbers.

(6) The marks of 15 students (out of 50) in an examination are

20, 22, 26, 31, 40, 19, 17, 19, 25, 29, 23, 17, 24, 21, 35

Find the median marks.

(7) The ages (in years) of 10 teachers in a school are

34, 37, 53, 46, 52, 43, 31, 36, 40, 50.

Find the median age.

(8) Find the median weight for the following data:

Weight (in kg)	45	46	48	50	52	54	55
Number of boys	8	5	6	9	7	4	2

Weight (in kg) (xi)	Number of boys (fi)	Cumulative frequency
45	8	8
46	5	13
48	6	19
50	9	28
52	7	35
54	4	39
55	2	41

Number of terms, n = 41; which is an odd number.

Median = (41+1)/2 th observation

Median = 21th observation.

Median = 50 kg.

(9) Calculating the median for the following data:

Marks	17	20	22	15	30	25
Number of students	5	9	4	3	10	6

Marks (xi)	Number of students (fi)	Cumulative frequency
17	5	5
20	9	14
22	4	18
15	3	21
30	10	31
25	6	37

Number of terms, n = 37; which is an odd number.

Median = (37+1)/2 th observation

Median = 19 th observation.

Median = 22

(10) the height (in cm) of 50 students of a class are given below:

Height (in cm)	156	154	155	151	157	152	153
Number of students	8	4	10	6	7	3	12

Find the median height.

Height (in cm)  (xi)	Number of students (fi)	Cumulative frequency
156	8	8
154	4	12
155	10	22
151	6	28
157	7	35
152	3	38
153	12	50