Stan invested $5,000, part 8% and part 17%. If the total interest at the end of the year is $490, how much did

Question

invest at 8%?

Answer 1

OK, set this up as two equations:
x + y = $5000 (splitting into 2 amounts)
0.08x + 0.17y = $490 (defining x as being invested at 8%, y at 17%)

Step 1: Use x + y = $5000 to define y.
y = 5000 - x

Step 2: Substitute your definition for y in equation 2.
0.08x + 0.17y = $490
0.08x + 0.17(5000-x) = $490
.08x - .17x + .17 * 5000 = 490
-.09x + 850 = 490
360 = .09x
$4000 = x (solution for 8%)
y = 5000 - x = 5000 - 4000 = $1000 (solution for 17%)

Check:
4000 * .08 + 1000 * .17 = 490
320 + 170 = 490 (check!)