Question

67 Average of 3 numbers is 7 and the average of 2 of them is 4. Then the 3rd
number is :
(a) 13
(b) 12
(c) 11
(d) 10
​

Answer 1

The sum of three numbers is 7 \times 3 = 21,

and the sum of first two numbers is 2 \times 4 = 8

Then the third number is 21 – 8 = 13.

Hence option (a) is the right answer.