A total of $15, 000 is invested in two corporate bonds that pay 5% and 7% interest. The investor wants to earn $880 in interest per year from the bonds. How much should be invested in at 7% to earn this interest?

$6500

Explanation:

Let the amount invested in 5% be X

Let the amount invested in 7% be 15000 - X

Therefore,

Given that interest from both is 880

We have

5x + 7(15000 - x) = 880 × 100

5x + 105000 - 7x = 88000

Collect like terms,

-2x = - 17000

x = 17000 ÷ 2

x = 8500

Therefore,

At 7%, amount invested

= 15000 - 8500

= $6500