First, we will look at a money word problem involving calculating Simple Interest. Simple Interest word problems are based on the formula for Simple Interest and the formula for Amount. Then, we will look at a money word problem that involves coins and dollar bills.
The following diagram gives the Simple Interest Formula. Scroll down the page for more examples and solutions on how to use the Simple Interest Formula to solve simple interest word problems.
Formula for Simple Interest
i = prt
i represents the interest earned.
p represents the principal which is the number of dollars invested.
r represents the interest rate per year.
t represents the time the money is invested which is generally stated in years or fractions of a year.
Formula for Amount
A represents what your investment is worth if you consider the total amount of the original investment (p) and the interest earned (i)
Example:
James needs interest income of $5,000. How much money must he invest for one year at 7%? (Give your answer to the nearest dollar)
Solution:
5,000 = p(0.07)(1)
p = 71,428.57
He must invest $71,429
Example:
Paul has $31.15 from paper route collections. He has 5 more nickels than quarters and 7 fewer dimes than quarters. How many of each coin does Paul have?
Solution:
Let x be the number of quarters
x + 5 be the number of nickels
x – 7 be the number of dimes
25x + 5(x + 5) + 10(x – 7) = 3,115
25x + 5x + 25 + 10x – 70 = 3,115
40x = 3,160
x = 79
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