SOLUTION: a stock broker has money in three accounts. the interest rates on the three accounts are 8%, 9%, and 10%. if she has twice as much money invested at 9% as she has invested in 8% th
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Question 1126112: a stock broker has money in three accounts. the interest rates on the three accounts are 8%, 9%, and 10%. if she has twice as much money invested at 9% as she has invested in 8% three times as much at 10% as she has at 8%and the total interest for the year is $280, how much is invested at each rate hint x is the amount invested at 8% Answer by ikleyn(52788) (Show Source):
Let x be the amount (in dollars) invested at 8%.
Then 2x dollars were invested at 9% and 3x dollars were invested at 10%.
Your equation is
interest + interest + interest = total interest, or
0.08x + 0.09*(2x) + 0.10*(3x) = 280 dollars.
Simplify and solve for x:
0.08x + 0.18x + 0.3x = 280
0.56x = 280
x = = 500.
Answer. $500 invested at 8%; $1000 invested at 9% and $1500 invested at 10%.
Solved.
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It is a standard and typical problem on investments.
You will find there different approaches (using one equation or a system of two equations in two unknowns), as well as
different methods of solution to the equations (Substitution, Elimination).
