Frank has decided to invest $8000 into two different funds. His RRSP pays interest at a rate of 9%/a, and his GASP pays at a rate of 6%/a. If he earned $615 of interest after one year, how much did he originally invest into each account?
Say, x amount is invested at 9% interest rate.
Say the interest earned = I1
"I1 = \\frac{x * 9}{100}"
"Or I1 = \\frac{9x}{100}"
And, Therefore, 8000-x will be invested at 6% interest rate.
Say the interest earned = I2
"I2 = \\frac{(8000-x) * 6}{100}"
"Or I2 = \\frac{48000 - 6x)}{100}"
Given, I1 + I2 = 615
"\\frac{9x}{100} + \\frac{48000-6x}{100} = 615"
Or
9x + 4800 - 6x = 61500
Or
3x = 61500 - 48000
Or
x = 4500
Final Answer: Amount x = 4500 is invested at 9% and balance 3500 ( = 8000-4500) is invested at 6%.
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