The average of 8 consecutive even numbers written in ascending order is 17. What is the average of the last three numbers, 36 and 53 ?

31

Let's assume numbers are x, x+2, x+4...............x+14

Sum of all numbers are = 8x + (2 + 4 + 6....... 14) = 8x + 56

As, S = n/2[2a + (n − 1) × d]   ....... (Airthmetic Progression)

As per given avg. sum of = 17 x 8 = 136

8x + 56 = 136

x = 10

So, last three no. are 20, 22 & 24

So sum of last three no. and 36 and 53 is = 155

So sum of last three no. and 36 and 53 is = 31