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Phyllis invested $8,500, a portion earning a simple interest rate?
Phyllis invested $8,500, a portion earning a simple interest rate of 9 1/5
% per year and the rest earning a rate of 9% per year. After 1 year the total interest earned on these investments was $777. How much money did she invest at each rate?
9 1/5 and 9?
2 Answers
- ?Lv 57 years agoFavorite Answer
change interest to decimals:
9% --> .09 9& 1/5 ---> .092
so....
let 'x' be the amount invested @ .092
.092x + .09( 8500 - x) = 777
.092x + 765 - .09x = 777
765 + .002x = 777
.002x = 12
x = 6000
the answer is 6000 and 2500
- BattleaxeLv 77 years ago
Let x be the amount invested at 9.2% and y the amount invested at 9%.
x + y = 8500 or y = 8500 - x
0.092x + 0.09y = 777
substitute first equation into second equation:
0.092x + 0.09(8500 - x) = 777
0.092x + 765 - 0.09x = 777
0.002x = 12
x = 12/0.002 = 6000
using first equation:
y = 8500 - 6000 = 2500
check using second equation:
0.092(6000) + 0.09(2500) = 777
552 + 225 = 777 checks
She invests $6000 at 9.2% and $2500 at 9%.
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