We prepare the cumulative frequency table, as shown below:
Let x and y be the missing frequencies of class intervals 3500 – 4500 respectively.
Then, 25 + x + y = 60 ⇒ x + y = 35 ……(1)
Median is 5000, which lies in 4500 – 5500. So, the median class is 4500 – 5500.
∴ l = 4500, h = 1000, N = 60, f = y and c f = 5 + x
Now,
⇒ y = 50 – 2x
⇒ 35 – x = 50 – 2x [From (1)]
⇒ 2x – x = 50 – 35
⇒ x = 15
∴ y = 35 – x [From (1)]
⇒ y = 35 – 15
⇒ y = 20
Hence, x = 15 and y = 20.