The average of a, b and c is 35 and the average of a, c and d is 40. If d = 25, then find the value of b.

Correct option is B

Given:

Average of a,b and c =35

Average of a,c and d =40

d= 25

Formula Used:

​$$Average = \frac{Sum\ of \ observations}{Number\ of \ observations}$$​​

Solution:

Total of a,b and c = $$35 \times 3$$​ = 105

Total of a,c and d = $$40 \times 3$$​ = 120

a+b+c = 105   ….(1)

a+c+d = 120   ….(2)

Subtracting eq(2) from (1) we get:

b - d = -15

b - 25 = -15

b = -15+25 = 10