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Suppose $70,000 is divided into two bank accounts. One account pays 10% simple interest per year and the other pays 5% simple interest. After three years, there is a total of $1,451.25 in interest between the two accounts. How much was invested into each account (rounded to the nearest cent)?

 Dec 30, 2018
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The initial investment must be a typo.  Even 1 year of 5% interest on 70k is 3.5k which is much larger than 1451.25

I'll assume OP meant 7000

 

\(P_1 = x,~P_2 = 7000-x\\ I = P_1 r_1 N + P_2 r_2 N = (0.1)3x + (0.05)3(7000-x) = 1451.25\)

 

\(1050+0.15x = 1451.25\\ 0.15x = 401.25\\ x = 2675\\ 7000-2675 = 4325\\ \text{so \$2675 was invested in the 10% account and \$4325 was invested in the 5% account}\)

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 Dec 30, 2018

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