Here are the step-by-step solutions for the problems on your worksheet.
1. $300 at 7.5% for 5 years
*
Formula: Interest = Principal × Rate × Time
*
Convert rate: 7.5% becomes 0.075.
*
Calculate: $300 \times 0.075 \times 5$
* $300 \times 0.075 = 22.5$
* $22.5 \times 5 = 112.5$
*
Answer: $112.50
2. $770 at 16% for 6 months
*
Convert time: Since the rate is per year, we must change 6 months into years. 6 months is half a year, so $t = 0.5$.
*
Convert rate: 16% becomes 0.16.
*
Calculate: $770 \times 0.16 \times 0.5$
* $770 \times 0.16 = 123.2$
* $123.2 \times 0.5 = 61.6$
*
Answer: $61.60
3. $668 at 9.25% for 15 months
*
Convert time: Divide months by 12 to get years. $15 \div 12 = 1.25$ years.
*
Convert rate: 9.25% becomes 0.0925.
*
Calculate: $668 \times 0.0925 \times 1.25$
* $668 \times 0.0925 = 61.79$
* $61.79 \times 1.25 = 77.2375$
*
Round: Round to the nearest cent ($77.24).
*
Answer: $77.24
4. $285 at 8.5% for 2 ½ years
*
Convert time: 2 ½ years is 2.5 years.
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Convert rate: 8.5% becomes 0.085.
*
Calculate: $285 \times 0.085 \times 2.5$
* $285 \times 0.085 = 24.225$
* $24.225 \times 2.5 = 60.5625$
*
Round: Round to the nearest cent ($60.56).
*
Answer: $60.56
5. $360 at 185% for 2 years
*
Convert rate: 185% becomes 1.85 (this is a very high interest rate!).
*
Calculate: $360 \times 1.85 \times 2$
* $360 \times 1.85 = 666$
* $666 \times 2 = 1332$
*
Answer: $1,332.00
6. $175 at 5.45% for 30 months
*
Convert time: $30 \div 12 = 2.5$ years.
*
Convert rate: 5.45% becomes 0.0545.
*
Calculate: $175 \times 0.0545 \times 2.5$
* $175 \times 0.0545 = 9.5375$
* $9.5375 \times 2.5 = 23.84375$
*
Round: Round to the nearest cent ($23.84).
*
Answer: $23.84
7. Sarah invested $150 at 8% simple interest. What is the total amount of money after 3 years?
* First, find the interest earned: $150 \times 0.08 \times 3$
* $150 \times 0.08 = 12$
* $12 \times 3 = 36$ (Interest is $36)
* Next, add the interest to the original investment (Principal) to get the Total Amount.
* $150 + 36 = 186$
*
Answer: $186.00
8. Ben borrowed $800 at 9% simple interest for 2 years. What is the total amount he must repay?
* First, find the interest owed: $800 \times 0.09 \times 2$
* $800 \times 0.09 = 72$
* $72 \times 2 = 144$ (Interest is $144)
* Next, add the interest to the amount borrowed to find the total repayment.
* $800 + 144 = 944$
*
Answer: $944.00
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Final Answer:
1. $112.50
2. $61.60
3. $77.24
4. $60.56
5. $1,332.00
6. $23.84
7. $186.00
8. $944.00
Parent Tip: Review the logic above to help your child master the concept of simple interest and compound interest worksheet.
