One half of the sum of three consecutive multiples of 10 is 90. What are the multiples of 10?

Answer 1

first represent the unknowns using variables.
let x = first multiple of 10
since consecutive multiples of ten has difference of 10 (example 40 and 30 has a difference of 10),
let x + 10 = second multiple of 10
let x + 20 = third multiple of 10
then we set-up the equation. from the first statement of the problem,
(1/2)*(x + x + 10 + x + 20) = 90
then we solve for x:
(1/2)*(3x + 30) = 90
3x + 30 = 180
3x = 150
x = 50 (first multiple)
x + 10 = 60 (second multiple
x + 20 = 70 (third multiple)

hope this helps~ :)