Question

The mean of the following frequency distribution is 50, and sum of all the
frequencies is 120. Find value of x and y.
20-40
Class
frequency
0-20
17
40-60
32
60-80
у
80-100
19
Total
120
Х​

Answer 1

Answer:

∑f

i

=68+p+q ∑f

i

x

i

=3480+30p+70q

⇒ ∑f

i

=120 [ Given ]

⇒ ∑f

i

=68+p+q

∴ 68+p+q=120

⇒ p=52−q ------- ( 1 )

Mean=

∑f

i

∑f

i

x

i

50=

120

3480+30p+70q

6000=3480+30p+70q

2520=30(52−q)+70q [ From ( 1 ) ]

2520=1560−30q+70q

960=40q

∴ q=24

Substituting value of q=24 in equation ( 1 ) we get,

∴ p=28