Question

A total of $7000 is invested: part at 7 % and the remainder at 15 %. How much is invested at each rate if the annual interest is $510?

Answer 1

The total invested = $7000

Part of the money at 7% and the reminder at 15%

Let the part at 7% = x

So, the part at 15% = 7000 - x

Given the annual interest = $510

so,

7% of x + 15% of ( 7000 - x ) = 510

0.07 * x + 0.15 * ( 7000 - x ) = 510

0.07 x + 0.15 * 7000 - 0.15 x = 510

0.07 x + 1050 - 0.15x = 510

0.07 x - 0.15 x = 510 - 1050

-0.08 x = - 540

divide both sides by -0.08

x = -540/-0.08 = 6,750

7000 - x = 7000 - 6750 = 250

So, the part that is invested at a rate of 7% = $6,750

And the part that invested at a rate of 15% = $250