The missing frequency marked x of the above distribution whose mean is 27 is :

Question

Class	0–10	10–20	20–30	30–40	40–50
Frequency	5	x	15	16	6

The missing frequency marked x of the above distribution whose mean is 27 is :

(a) 7

(b) 8

(c) 9

(d) 10

Answer 1

Correct option is (b) 8

Class	Frequency (f)	Class Mark (x)	fx
0-10	5	5	25
10-20	x	15	15x
20-30	15	25	375
30-40	16	35	560
40-50	6	45	270
Total	42 + x		1230 + 15x

Given, Mean = \(\frac{\sum fx}{\sum f} = 27\)

⇒ \(\frac{1230 + 15x}{42 + x} = 27\)

⇒ \(1230 + 15 x = 1134 + 27 x\)

⇒ \(96 = 12 x\)

⇒ \(x = 8\)

Answer 2

(5x5 + 15xn + 15x25 + 35x16 + 45x6)/(5 + n + 15 + 16 + 6) = 27

n = 8

The missing frequency marked x of the above distribution whose mean is 27 is : (b) 8