SOLUTION: At simple interest a sum of money amounted to $2668.75 in 9 months and to $2800 in 16 months. Find the amount of money invested and the rate. I am missing something: i belie

Question 950981: At simple interest a sum of money amounted to $2668.75 in 9 months and to $2800 in 16 months. Find the amount of money invested and the rate.
I am missing something:

i believe that the P and R in I=PRT are the same, but can't seem to solve the problem. Thanking you in advance!
Answer by macston(5194) (Show Source): You can put this solution on YOUR website!
The difference in the two amounts is simple interest on the original principal for 7 months.:$2800-2668.75=$131.25 $131.25/7 mos=$18.75/mo
$18.75/mo*9 mo=$168.75 $2668.75-$168.75=$2500
ANSWER 1: The original sum invested was $2500
CHECK:
$18.75/mo*16 mo=$300 $2800-$300=$2500
PART 2: INTEREST RATE
($18.75/$2500)(100 %)=0.75%/mo ANSWER 2: The interest rate is 0.75% per month.

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