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Applications of Percents in Word Problems Practice Questions

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Updated on Oct 4, 2011

To review these concepts, go to Applications of Percents in Word Problems Study Guide.

Applications of Percents in Word Problems Practice Questions

Problems

  1. Pat makes 3% commission on his total weekly sales. If his weekly sales total $2,350, what is his amount of commission earned?
  2. What is the total cost of an item that is marked $20.00 if the sales tax is 8%?
  3. What is the sale price of a new computer that costs $450.00 if the amount of discount is 25% off?
  4. If a 15% tip was left for a server, what was the amount of the tip in dollars if the total cost of the meal was $24?
  5. The price of a gallon of gasoline increased from $2.50 a gallon to $2.75 a gallon. What was the percent of increase?
  6. John's electric bill went from $68 last month to $54.40 this month. What was the percent of decrease in his bill?
  7. What is the total amount of interest paid on a $150 loan with an 8% interest rate and a time of 2 years?
  8. Henry earns $50 interest on money he invested at a 5% interest rate for 6 months. How much money did he invest?

Solutions

  1. Read and understand the question. This question is looking for the amount of commission earned. The percent of commission and total sales are given.
  2. Make a plan. To find the commission, use the proportion .

    Carry out the plan. Substitute the values, and the proportion becomes . Cross multiply to get 100x = 7,050. Divide each side of the equation by 100 to get

      x = $70.50

    Pat made $70.50 in commission.

    Check your answer. To check this problem, divide the answer of $70.50 by $2,350 to be sure the commission rate comes out to be 3%: 70.50 ÷ 2,350 = 0.03 = 3%. This solution is checking.

  3. Read and understand the question. This question is asking for the total cost of an item that is marked $20.00 if the tax that needs to be added is 8% of this price.
  4. Make a plan. To find the sales tax, use the proportion . Then, add this amount to $20.00 for the final answer

    Carry out the plan. Substitute the values, and the proportion becomes . Cross multiply to get 100x = 160. Divide each side of the equation by 100 to get

      x = $1.60

    The tax is $1.60. Thus, the total cost is $20.00 + $1.60 = $21.60.

    Check your answer. To check this answer, divide the amount of tax by $20.00 to be sure that the tax rate is 8%: 1.60 ÷ 20 = 0.08 = 8%. This answer is checking.

  5. Read and understand the question. This question is looking for the sale price when a discount of 25% is given.
  6. Make a plan. To find the sale price, first find the amount of discount. Use the proportion . Then, subtract the discount from the original cost to find the sale price.

    Carry out the plan. Substitute into the proportion and get . Cross multiply to get 100x = 11,250. Divide each side of the equation by 100 to get

      x = $112.50

    The discount is $112.50. Thus, the total sale price will be $450 – $112.50 = $337.50.

    Check your answer. To check this answer, divide the amount of discount by 450 to be sure it is 25% of the original price: 112.50 ÷ 450 = 0.25 = 25%. This solution is checking.

  7. Read and understand the question. This question asks for the amount of tip when the percent is 15%.
  8. Make a plan. To find the amount of tip, use the proportion .

    Carry out the plan. Substitute into the proportion and get . Cross multiply to get 100x = 360. Divide each side of the equation by 100 to get

      x = $3.60

    They should leave $3.60 as a tip for the server.

    Check your answer. To check this answer, divide the amount of the tip by $24 to be sure it is 15% of the original price: $3.60 ÷ $24 = 0.15 = 15%. This answer is checking.

  9. Read and understand the question. This question is looking for the percent of increase in the cost of a gallon of gasoline.
  10. Make a plan. To solve this problem, use the proportion . Subtract the two given amounts to find the difference.

    Carry out the plan. Subtract the amounts to find the difference: $2.75 – $2.50 = $0.25. Substitute into the proportion and get . Cross multiply to get 2.5x = 25. Divide each side of the equation by 2.5 to get

      x = 10

    The percent of increase is 10%.

    Check your answer. Substitute the solution into the proportion to check this answer. The proportion is . The cross products are each 25, so this answer is checking.

  11. Read and understand the question. This question asks for the percent of decrease between John's electric bills.
  12. Make a plan. To solve this problem, use the proportion . Subtract the two given amounts to find the difference.

    Carry out the plan. Subtract the amounts to find the difference: $68 – $54.40 = $13.60. Substitute into the proportion and get . Cross multiply to get 68x = 1,360. Divide each side of the equation by 68 to get

      x = 20

    The percent of decrease is 20%.

    Check your answer. Substitute the solution into the proportion to check this answer. The proportion is . The cross products are each 1,360, so this answer is checking.

  13. Read and understand the question. This question is asking for the amount of interest on a loan after 2 years.
  14. Make a plan. Use the formula I = p × r × t, and substitute the given values.

    Carry out the plan. In this problem, the principle (p) is $150, the interest rate (r) is 8%, and the time (t) is 2 years. Substitute each value into the formula. Don't forget to change the percent to a decimal. The formula becomes I = (150)(0.08)(2) = $24. The interest earned is $24.

    Check your answer. To check this answer, divide the amount of interest by the principle and the rate to see if the result is the time of 2 years: = 2 years. This question is checking.

  15. Read and understand the question. This question is asking for the amount of principle on an investment of 6 months.
  16. Make a plan. Use the formula I = p × r × t and substitute the given values.

    Carry out the plan. In this problem, the principle (p) is unknown, the interest rate (r) is 5%, and the time (t) is 6 months, or 0.5 years. This time, the interest (I) is given as $50. Substitute each value into the formula. Don't forget to change the percent to a decimal. The formula becomes 50 = (p)(0.05)(0.5). Multiply on the left side of the equation: 50 = 0.025p. Divide each side of the equation by 0.025.

      2,000 = p

    The principle is $2,000.

    Check your answer. To check this answer, divide the amount of interest by the principle and the rate to see if the result is the time of 0.5 years: = 0.5 years. This answer is checking.

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