SOLUTION: Mr. Jones has $10,000 to invest. He invests part at 6% and the rest at 8%. If he earns $680 in interest after 1 year, how much did he invest at each rate?
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Question 1111406: Mr. Jones has $10,000 to invest. He invests part at 6% and the rest at 8%. If he earns $680 in interest after 1 year, how much did he invest at each rate? Answer by ikleyn(52776) (Show Source):
Your equation is
0.06*x + 0.08*(10000-x) = 680,
where "x" is the amount of the 6% investment.
Solve for x:
0.06x + 800 - 0.08x = 680
-0.02x = 680 - 800 = -120 ====> x = = 6000.
Answer. $6000 was invested at 6%. The rest $10000-$6000 = $4000 was invested at 8%.
Check. 0.06*6000 + 0.08*4000 = 680 dollars. ! Correct !
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).
