Problema Solution
Mary invested one amount at 10% simple interest, and a second amount at 3% interest, earning $21.72 in one year. If she had switched the amounts, she would have earned $15.07. What were the two amounts?
Answer provided by our tutors
Let first amount = x
Let second amount = y
.1x+0.03y = 21.72
.03x+0.1y = 15.07
=> .03x + 0.009y = 6.516
subtracting the above equation from second we get
0.091y = 8.554 => y = 94
=> x = 189