Decimals and percentages · Ages 11–12

Simple interest worksheet

Part of: Percentages

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Decimals and percentages · Ages 11–12

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Write each answer in the space. For word problems, show your working and write a sentence answer.

1.$1,000 is put in a bank at 6% a year. How much interest does it earn in one year?
Answer:
2.$200 is put in a bank at 5% a year. How much interest does it earn in one year?
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3.$7,500 is put in a bank at 1% a year, simple interest. How much is there after 5 years, money and interest together?
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4.$1,500 is put in a bank at 1% a year, simple interest. How much interest does it earn in 3 years?
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5.$9,500 is put in a bank at 1.5% a year, simple interest. How much interest does it earn in 3 years?
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6.$8,000 is put in a bank at 5% a year, simple interest. How much is there after 4 years, money and interest together?
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7.Some money is put in a bank with simple interest: after 1 year there is $8,080, after 2 years $8,160 and after 3 years $8,240, money and interest together. Going on like this, how much is there after 10 years?
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8.Some money is put in a bank with simple interest: after 1 year there is $6,240, after 2 years $6,480 and after 3 years $6,720, money and interest together. Going on like this, how much is there after 10 years?
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9.$9,000 is put in a bank at 6% a year, simple interest. Which calculation gives the interest for 6 years?
- A. 9000 + 9000 × 6% × 6
- B. 9000 × 6%
- C. 9000 × 6% × 6
- D. 9000 × 6 × 6
Choose the right answer
Answer:
10.$8,000 is put in a bank at 6% a year, simple interest. Which calculation gives the interest for 3 years?
- A. 8000 + 8000 × 6% × 3
- B. 8000 × 6% × 3
- C. 8000 × 6 × 3
- D. 8000 × 6%
Choose the right answer
Answer:
11.$2,000 is put in a bank at 5% a year, simple interest. After 4 years there is $2,400 in all, money and interest together.
True or false?
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12.$7,000 is put in a bank at 3% a year, simple interest. After 5 years there is $7,210 in all, money and interest together.
True or false?
Answer:

13.Ka-lok's uncle borrows $35,000 from a bank at 4% a year, simple interest, and pays it all back with the interest after 2 years. How much does he pay back in all?
Working:
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14.Tsz-hin puts $1,500 of lai see money in a bank at 4% a year, simple interest. How much can Tsz-hin take out after 5 years, money and interest together?
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15.Tsz-hin's grandpa wants $1,500 of interest a year from the bank. At 5% a year, simple interest, how much must he put in?
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16.Tsz-hin's aunt puts $14,000 in a bank at 5% a year, simple interest. How many years until the interest comes to $5,600?
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17.Bank A pays 2% a year and Bank B 3%, both simple interest. Keeping $3,000 for 5 years, how much more interest does Bank B pay than Bank A?
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18.Tsz-ching's aunt puts $3,000 in a bank at 2% a year, simple interest. How many years until the interest comes to $120?
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Show the answers and working

Simple interest worksheet: Answers and working

1. 60 dollars
A year's interest = money × yearly rate, so find 6% of 1000.
Interest = money × yearly rate: 1000 × 6100 = 60.
2. 10 dollars
A year's interest is 5% of 200. First think what 1% of 200 is.
Interest = money × yearly rate: 200 × 5100 = 10, so a year's interest is $10.
3. 7,875 dollars
Find the interest for 5 years first, then add back the 7500.
Interest for 5 years: 7500 × 1100 × 5 = 375; 7500 + 375 = 7875.
4. 45 dollars
Find one year's interest first, 1% of 1500, then think about 3 years.
Each year: 1500 × 1100 = 15; 3 years: 15 × 3 = 45.
5. 427.5 dollars
Find one year's interest first, 1.5% of 9500, then think about 3 years.
Each year: 9500 × 1.5100 = 142.5; 3 years: 142.5 × 3 = 427.5.
6. 9,600 dollars
Find the interest for 4 years first, then add back the 8000.
Interest for 4 years: 8000 × 5100 × 4 = 1600; 8000 + 1600 = 9600.
7. 8,800 dollars
How much is added each year? Work out 8160 − 8080: that's a year's interest.
Then take a year's interest from the 8080 after 1 year to find the money put in.
Each year adds 8160 − 8080 = 80; the money put in was 8080 − 80 = 8000; after 10 years: 8000 + 80 × 10 = 8800.
8. 8,400 dollars
How much is added each year? Work out 6480 − 6240: that's a year's interest.
Then take a year's interest from the 6240 after 1 year to find the money put in.
Each year adds 6480 − 6240 = 240; the money put in was 6240 − 240 = 6000; after 10 years: 6000 + 240 × 10 = 8400.

9. C. 9000 × 6% × 6
Interest = money × yearly rate × years. Which has all three, without the money added on?
Interest = money × yearly rate × years: 9000 × 6% × 6 = 3240.
10. B. 8000 × 6% × 3
Interest = money × yearly rate × years. Which has all three, without the money added on?
Interest = money × yearly rate × years: 8000 × 6% × 3 = 1440.
11. True
Find a year's interest, times 4 years, and remember to add the money back. Then compare with 2400.
Interest is 100 a year, 400 in 4 years; with the money, 2000 + 400 = 2400.
12. False
Find a year's interest, times 5 years, and remember to add the money back. Then compare with 7210.
Interest is 210 a year, 1050 in 5 years; with the money, 7000 + 1050 = 8050.

Marking: 2 for the working, 1 for the answer, 1 for the sentence.

13. 37,800 dollars
Find the interest for 2 years first, then add the 35000 borrowed.
Interest: 35000 × 4100 × 2 = 2800; he pays back 35000 + 2800 = 37800.
14. 1,800 dollars
Find the interest for 5 years first, 4% of 1500 each year, then add the money back.
Interest: 1500 × 4100 × 5 = 300; 1500 + 300 = 1800.
15. 30,000 dollars
The $1,500 a year is 5% of the money put in. Work back from there.
A year's interest is 5% of the money: money = 1500 ÷ 5 × 100 = 30000.
16. 8 years
Find one year's interest first: 5% of 14000.
Each year: 14000 × 5100 = 700; 5600 ÷ 700 = 8 years.
17. 150 dollars
The money and the years are the same at both banks; only the rates differ, by 3% − 2%.
A: 3000 × 2100 × 5 = 300; B: 3000 × 3100 × 5 = 450; the difference is 150.
18. 2 years
Find one year's interest first: 2% of 3000.
Each year: 3000 × 2100 = 60; 120 ÷ 60 = 2 years.

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