Answer:
The amount invested at 9% is $93000
The amount invested at 10% is $303000
Step-by-step explanation:
Let the amount invested at 9% interest rate be x
And the amount invested at 10% rate be y
Simple Interest from x in a year = 0.09x
Simple Interest from y in a year = 0.1y
But y = 24000 + 3x
And the sun of the interests, 0.09x + 0.1y = 38670
Now we have a simultaneous eqn
y = 24000 + 3x (eqn 1)
0.09x + 0.1y = 38670 (eqn)
Substitute y into eqn 2
0.09x + 0.1(24000 + 3x) = 38670
0.09x + 2400 + 0.3x = 38670
0.39x = 38670 - 2400
x = 36270/0.39 = $93000
y = 24000 + 3x = 24000 + 3 × 93000 = $303000