Percentages and ratio · Ages 12–13

Simple and compound interest worksheet

Part of: Percentages (I)

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Percentages and ratio · Ages 12–13

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Name:Date:Score:／48

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

1.Principal $2,000 at 5% a year for 2 years: one year's interest = $, the simple interest for 2 years = $, the amount = $.
Fill in each blank
Answer:
2.Principal $9,000 at 7.5% a year for 4 years: simple interest = $
Answer:
3.Principal $6,000 at 4.5% a year for 3 years: one year's interest = $, the simple interest for 3 years = $, the amount = $.
Fill in each blank
Answer:
4.Principal $5,000 for 6 years earns $600 simple interest: the yearly rate = %
Answer:
5.Principal $11,200 at 3% a year for 9 months: simple interest = $
Answer:
6.Principal $8,400 at 2% a year for 6 months: simple interest = $
Answer:
7.Principal $14,000 at 6% a year, compounded yearly. The amount after 2 years = $
Answer:
8.A principal of $5,000 at 8% a year earned $2,800 in simple interest. For how many years?
Answer:

9.On $8,000 at 6% a year, the simple interest for 3 years is $480.
True or false?
Answer:
10.A principal of $4,000 at 5% a year for 2 years: what is the simple interest?
- A. $4,400
- B. $400
- C. $200
- D. $410
Choose the right answer
Answer:
11.On $5,000 at 6% a year, the simple interest for 3 years is $300.
True or false?
Answer:
12.A principal of $1,000 at 2% a year for 2 years: what is the simple interest?
- A. $20
- B. $40.4
- C. $1,040
- D. $40
Choose the right answer
Answer:

13.Tsz-ching saves $25,000 at 6% a year simple interest for 3 years. Interest = $, amount = $.
Fill in each blank
Working:
Answer:
14.A principal of $2,000 at simple interest grows to $2,200 in 5 years. Find the rate: put the steps in order.
- A. a year's interest = 200 ÷ 5 = 40
- B. interest = 2200 − 2000 = 200
- C. rate = 40 ÷ 2000 × 100% = 2%
Write the letters in the right order
Working:
Answer:
15.Ka-yan's mum saves $10,000 at 2% a year, compounded yearly. How much interest is earned in 3 years?
Working:
Answer:
16.A principal of $8,000 at simple interest grows to $8,960 in 6 years. What is the yearly rate?
Working:
Answer:
17.Someone borrows $27,000 at 2% a year simple interest. How much is owed after 5 years?
Working:
Answer:
18.A principal of $10,000 at 2% a year simple interest. After how many years is the amount $12,200?
Working:
Answer:

Show the answers and working

Simple and compound interest worksheet: Answers and working

1. 100, 200, 2,200
2000 × 5% = 100; 100 × 2 = 200; 2000 + 200 = 2200.
2. 2,700
Interest = principal × rate × years = 9000 × 7.5% × 4 = 2700.
3. 270, 810, 6,810
6000 × 4.5% = 270; 270 × 3 = 810; 6000 + 810 = 6810.
4. 2
5000 × r% × 6 = 600, so r% = 600 ÷ 30000, and r = 2.
5. 252
A yearly rate needs years: 9 months = 0.75 years, and 11200 × 3% × 0.75 = 252.
6. 84
A yearly rate needs years: 6 months = 0.5 years, and 8400 × 2% × 0.5 = 84.
7. 15,730.4
14000 × 1.06 = 14840, then 14840 × 1.06 = 15730.4. The second year's interest is on 14840, so it beats simple interest.
8. 7 years
A year's interest is 5000 × 8% = 400, and 2800 ÷ 400 = 7 years.

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

13. 4,500, 29,500
25000 × 6% × 3 = 4500, and the amount is 25000 + 4500 = 29500.
14. B → A → C
Amount less principal is the interest; then a year's share; then divide by the principal.
15. 612.08 dollars
Amount = 10000 × 1.02 × 1.02 × 1.02 = 10612.08, and the interest = 10612.08 − 10000 = 612.08. It asks for the interest, so take the principal off.
16. 2%
Interest = 8960 − 8000 = 960, 160 a year, and 160 ÷ 8000 × 100% = 2%.
17. 29,700 dollars
The principal and the interest: 27000 + 27000 × 2% × 5 = 27000 + 2700 = 29700.
18. 11 years
The interest must be 12200 − 10000 = 2200, at 200 a year: 2200 ÷ 200 = 11 years.

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