Out of three numbers, the first is twice the second and is half of the third. If the average of the three numbers is 56, then the average of the first and the third number is -

Question: Out of three numbers, the first is twice the second and is half of the third. If the average of the three numbers is 56, then the average of the first and the third number is -

Solution:
Let, the second number be = x
So, the first number is = 2x
and the third number is = 2x × 2 = 4x

According to the question,
2x + x + 4x = 56 × 3
⇒ 7x = 168
⇒ x = 24

So, the first number is = 2 × 24 = 48
and the third number is = 4 × 24 = 96

Then, the average of the first and the third number is = (48 + 96)/2 = 72