Reuben invested his savings in two investment funds. The $4000 that he invested in Fund A returned a 10% profit. The amount that he invested in Fund B returned a 3% profit.

Question

Reuben invested his savings in two investment funds. The $4000 that he invested in Fund A returned a 10% profit. The amount that he invested in Fund B returned a 3% profit. How much did he invest in Fund B, if both funds together returned a 5% profit

Answer 1

3 is within 2 of 5

10 is within 5 of 5

he had 5/2 = 2.5 times as much invested at 3% as at 10%

4,000 x 2.5 = $10,000 invested at 3%

.03x + .10(4,000) = .05(4,000+x)

.05x -.03x = 400-200 = 200

.02 = 200

x = 200/.02 = $10,000 invested at 3%

.03(10) + .1(4) = .3+.4 = .7 = .05(14) in units of thousands of dollars

average return of 5% on 14 thousand total invested = $700 total return or profit

3% of 10 thousand = $300

10% of 4 thousand = $400

300+400 = 700