Q. The average of three numbers is 7 and that is of first two numbers is 4, then what is the third number?
Answer:
13
Notes: The sum of three numbers is 7 x 3 = 21, and the sum of first two numbers is 2 x 4 = 8
Then the third number is 21 – 8 = 13.
Hence option [B] is the right answer.