Question

Helene invested a total of $1000 in two simple-interest bank accounts. One account paid 5% annual interest; the other paid 7% annual interest. The total amount of interest she earned after 1 year was $60. Find the amount invested in each account.

Answer 1

x + y = 1000, (1)
0.05x + 0.06y = 58. (2)


From (1), express y = 1000-x and then substitute it into (2)

0.05x + 0.06*(1000-x) = 58

0.05x + 60 - 0.06x = 58

-0.01x = 58 - 60 = -2 ====> x = %28-2%29%2F%28-0.01%29 = 200%2F1 = 200.


Answer. $200 was invested at 5%. The rest $1000 - $200 = $800 was invested at 6%.


Check. 200*0.05 + 800*0.06 = 58. ! Correct !


Solved. // I used the Substitution method to solve the system of 2 equations in 2 unknowns.