Question

The mean of observations, given in the adjoining table, is 24, the value of a is:

x	f
10	10
20	a
30	30

पर्याय

• 20

• 30

• 10

• 25

Answer 1

10

Explanation:

x	f	fx
10	10	100
20	a	20a
30	30	900
Total	Σf = 40 + a	Σfx = 1000 + 20a

By formula,

\[\text{Mean} = \frac{\Sigma fx}{\Sigma f}\]

Substituting values we get :

\[\Rightarrow 24 = \frac{1000 + 20a}{40 + a}\]

⇒ 24(40 + a) = 1000 + 20a

⇒ 960 + 24a = 1000 + 20a

⇒ 24a - 20a = 1000 − 960

⇒ 4a = 40

⇒ a = 10