Problema Solution
Bob invested $9000 in two accounts, some of it at 4% simple interest, and the rest in an account earning 6% simple interest. How much did he invest in each account if he earned $275 interest after 1 year?
Answer provided by our tutors
let
x = the money invested at the 4% simple interest account, x>0
y = the money invested at the 6% simple interest account, y>0
Bob invested $9000 in two accounts
x + y = 9000
he earned $275 interest after 1 year
0.04*x + 0.06*y = 275
by solving the system of equations
x + y = 9000
0.04*x + 0.06*y = 275
we find
x = 13250
y = - 4250
the system doesn't have positive solutions for both x and y this means that it is impossible that Bob earned from the two accounts.
The scenario explained in the problem is possible if Bob earned 4% from $13,250 (the first account) and lost 6% from $4,250 (the second account).