Carolyn received a check last week . She invested part at 15% and 1000 more than this amount at 16%. If she will earn $780 in interest in a year, how much was invested at each rate?
Let the amount invested at 15% = A
Let the amount invested at 16% = A + 1000
So....
Interest = Prt where t =1
780 = .15A + .16 (A + 1000)
780 = .15A + .16A + 160
780 - 160 = .31A
.31A = 620
A = 620 / .31 = $2000 at 15%
And
A + 1000 = $3000 at 16%
