In a set of seven numbers, the average of the first for is 15 and the average of the last three is 8. What is the average of all 7 numbers

Question

anonymous · Answer

Find the total of the first four and to total of the last three.

jigglypuff314 · Answer

if you let   x represent the sum of the first four numbers
then  x/4 = 15     (multiply both sides by 4)
         *4       *4
        x = 15*4

and  let   y represent the sum of the last three numbers
then  y/3 = 8      (multiply both sides by 3)
         *3     *3
       y = 8*3

then they want to know
(x+y)/7 = ?
so plug in what you know

( 15*4  +  8*3 ) / 7 =?