There are four different numbers. The average of first three of them is four times the fourth number and the average of all the four numbers is 87.75. What is the average of the first three numbers?

108

Sum of 4 numbers = 4 × 87.75 = 351

Let 4th number = a

Average of first 3 numbers = 4a

Sum of first 3 numbers = 3 × 4a = 12a

ATQ ,

12a + a = 351

13a = 351

a = \(\frac{351}{13}\) = 27

Average of first 3 numbers = 4 × 27 = 108