Question

The average of 5 numbers is 9 and the average of the last three numbers is 5.Find the average of the first two numbers.

Answer 1

$\frac{a+b+c+d+e}{5}$=9-------------(1)
$\frac{c+d+e}{3}$=5
c+d+e=15------------(2)
Sub (2) into (1)
$\frac{a+b+15}{5}$=9
a+b+15=45
a+b=30