Question

A total of $12,000 is invested into two simple interest accounts. On one account the annual simple interest rate is 12%, while on the second account the annual interest rate is 18%. How much should be invested at 12% so that the interest earned is the same?

Answer 1

since 12% is 2/3 as much interest, 3/2 as much should be invested there.

Or, since the interest ratio is 2:3, the investment should be 3:2

So, 40% at 18% and 60% at 12%

.12 * 7200 = .18 * 4800 = 864

or, in the usual algebraic way,

.12x = .18(12000-x)