GMAT Math : Calculating simple interest
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Example Questions
Example Question #1 : Calculating Simple Interest
Grandpa Jack wants to help pay for college for his grandson, Little Jack. Little Jack is currently 8 years old. Grandpa Jack makes a one-time deposit into an account that earns simple interest every year. Grandpa Jack invests $10,000 now and in ten years, that will grow to $15,000. What rate of simple interest did Grandpa Jack receive?
6%
4%
2%
3%
5%
5%
To calculate simple interest, the formula is
 "FV= PV (1+it)")
where 
Solving this we get
or 5%
ALTERNATE SOLUTION:
Another way of finding this is to calculate the amount of interest per year. Since this is simple interest, Grandpa Jack earns the same amount of interest per year. The total interest earned is 15,000-10,000= 5,000. $5,000 over 10 years, equates to $500 per year. $500 divided by the original $10,000 is .05, or 5%.
Example Question #2 : Interest Problems
How much interest would an investment yield if the principal of 
Example Question #1 : Calculating Simple Interest
What rate does Johnny need if he would like to yield 
Example Question #2 : Calculating Simple Interest
A bank offers a business a loan in the amount of $13,000 with a simple annual interest rate of 9%. How much will the business owe the bank after 3 years?
The accrual of simple interest can be found in two steps. First, multiply the principal amount by the interest rate. Second, multiply that result by the number of years during which interest will accrue.
The question asks for the total amount that the business will owe the bank, so we must add the interest accrued to the principal amount.
Example Question #1 : Calculating Simple Interest
John has 
Simple interest formula:
Example Question #1 : Calculating Simple Interest
How many years would it take Marissa to make 
Simple interest formula is:
Therefore, solving for the time factor:
Example Question #5 : Calculating Simple Interest
Using the simple interest formula, what initial investment does Terry have to make to earn 
Simple interest formula:
Therefore, solving for the principal factor in the equation:
Example Question #4 : Interest Problems
What return does Florence have to yield in order to make 
Simple interest formula:
Therefore, solving for the rate factor in the equation:
Example Question #1 : Interest Problems
Jesse has 
Simple interest formula:
Example Question #3 : Calculating Simple Interest
How many years would it take Julissa to make 
Simple interest formula is:
Therefore, solving for the time factor:
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