Harrington received a 30,000 inheritance 6% and 9%

Question

Harrington received a $30,000 inheritance from his grandfather. For the first year he invested part of the money in an account 6% simple interest and the remainder of the money in an account at 9% simple interest. If he received $2100 in interest for the year, find the a lint invested in each account

Answer 1

Simple interest is just the amount times the percent (in decimals). If we let "x" be the amount Harrington invested at 6% (0.06), then "30,000 - x" will be the amount he invested at 9% (0.09) since he had a total of $30,000 to invest.The total interest he earned would be the amount he earned at 6% plus the amount he earned at 9% or:

0.06x + 0.09(30,000 - x) = 2100

0.06x + 2700 - 0.09x = 2100

-0.03x = - 600

x = 20,000

So he invested $20,000 at 6% simple interest and the rest ($10,000) at 9%.