Given Median =28.5
Then, median Class = 20 – 30
the lower limit (l) = 20
cumulative frequency of the class preceding 20 – 30 (cf) = 5 + x
frequency of the median class 20 – 30 = 20,
class size (h) = 10
Total frequencies (n) = 60
So, 45 + x + y = 60
⇒ x + y = 60 – 45
⇒ x + y = 15 …(i)
⇒8.5 × 2 = 25-x
⇒17 = 25 – x
⇒ x = 8
Putting the value of x in eq. (i), we get
⇒ 8 + y = 15
⇒ y = 15 – 8
⇒ y = 7