Finished: Math Practice Questions Air Class 3

1. Simple Interest Calculation (Revised for Clarity)

Maria invests $1,500 in a savings account with a 4% annual simple interest rate.

  • (a) How much interest will she earn after 3 years?
  • (b) How many years will it take for her total interest to reach $300?
    Steps:
  • if she earns 4 percent interest she will earn $60
  • so in 3 years she will earn 180
  • 300/60
  • 5
    Answer:
  • A = $180
  • b = 5 years

2. Profit and Loss on Bicycles

A shop buys 30 bicycles at $200 each. It sells 20 bicycles at a 25% profit and the remaining 10 bicycles at a 10% loss. What is the total profit or loss?
Steps:

profit of first 20 bikes is 20 * 200* 25% = 1000

loss of the 10 bikes is 10 *200 * 10% = 200

total profit = 1000-200 = 800


Answer: His total profit is 800 dollars

3. Marked Price and Discount

A pair of shoes was marked 40% above cost price but sold at a 15% discount. If the profit was $28, what was the original cost price?
Steps:

140%C=MP

85%MP= SP

SP-C = 28

-C=28-SP

C=SP-28

C =85%MP-28

C = 85% 1.4C - 28

C =1.19 C - 28

-0.19C=-28

0.19C=28

C=147.368421053

Answer: C=147.368421053

4. Comparing Two Sales (Profit vs. Loss)

A dealer sold two identical cars for $12,000 each. The first car was sold at a 20% profit, and the second car was sold at a 20% loss.

  • (a) Did the dealer make an overall profit or loss?
  • (b) By how much?
    Steps:
  • First car cost: $12,000 ÷ 1.2 = $10,000
  • profit $2,000
  • Second car cost: $12,000 ÷ 0.8 = $15,000
  • loss $3,000
  • total: -$1,000.
    Answer: a the man lost money b he lost 1000 dollars

5. Compound Interest vs. Simple Interest

  • Option 1: A bank offers 5% simple interest per year on a $2,000 deposit.
  • Option 2: Another bank offers 5% interest compounded annually on the same deposit.
    Calculate the difference in interest earned after 3 years between the two options.
    Steps:
  • with simple interest the man will earn 100 dollars a year so in 3 years he will earn 300 dollars worth of interest.
  • but with compound interest the man will earn 100 dollars for the first year so he will have 2100 dollars
  • and in the second year he will earn 105 dollars so he will have 2205 dollars
  • in the third and final year he will earn 110.25 dollars
  • so in the end he will earn 2315.25 dollars
  • 2315.25 - 2000 = 315.25
    Answer: with simple interest the man will earn 300 dollars but with compound interest he will earn 315.25
  • so the man will earn $15.25 more with compound interest.