Math 9 · Unit 3: Decimals, percentages and rounding · Cambridge Lower Secondary Maths Stage 9

Questions

1. 1. $300 is increased by 15%. What is the new amount?

   • $45
   • $315
   • $345
   • $255
   Check

2. 2. Copy and complete the workings for this percentage increase. $200 increased by 20%

   Fill the blanks with these.

   • 1.2
   • 0.2
   • 40
   • 240
   Check

3. 3. Copy and complete the workings for this percentage increase. $400 increased by 32%

   Fill the blanks with these.

   • 1.32
   • 0.32
   • 528
   • 128
   Check

4. 4. $300 is decreased by 15%. What is the new amount?

   • $255
   • $285
   • $45
   • $345
   Check

5. 5. Copy and complete the workings for this percentage decrease. $200 decreased by 20%

   Fill the blanks with these.

   • 160
   • 40
   • 0.2
   • 0.8
   Check

6. 6. Copy and complete the workings for this percentage decrease. $400 decreased by 32%

   Fill the blanks with these.

   • 272
   • 128
   • 0.32
   • 0.68
   Check

7. 7. Match each percentage change to its multiplier.

   • increase by 40%
   • decrease by 25%
   • decrease by 5%
   • increase by 4%
   • decrease by 62%

   • 0.38
   • 1.4
   • 0.95
   • 1.04
   • 0.75
   Check

8. 8. $800 is increased by 10%, then increased by 20%. What is the final amount?

   • $1056
   • $1040
   • $1000
   • $960
   Check

9. 9. Copy and complete the workings. $800 decreased by 10%, then decreased by 20%

   Fill the blanks with these.

   • 720
   • 0.8
   • 576
   • 560
   • 0.2
   Check

10. 10. Copy and complete the workings. $800 increased by 25%, then decreased by 40%

    Fill the blanks with these.

    • 0.75
    • 0.4
    • 1.25
    • 1000
    • 600
    • 0.6
    Check

11. 11. Copy and complete the workings. $800 increased by 5%, then decreased by 15%

    Fill the blanks with these.

    • 0.85
    • 1.05
    • 0.95
    • 840
    • 714
    • 0.15
    Check

12. 12. Work out these compound percentage changes. i 200 increased by 10%, then decreased by 10%. ii 200 decreased by 10%, then increased by 10%. What are the two results?

    • i 220 and ii 180
    • i 198 and ii 202
    • i 198 and ii 198
    • i 200 and ii 200
    Check

13. 13. Which sign is missing? 200 increased by 10% then decreased by 10% ☐ 200 decreased by 10% then increased by 10%

    • >
    • It depends.
    • =
    • <
    Check

14. 14. Without doing any calculations, decide which sign, <, > or =, is missing from each sentence. i 40 decreased by 30%, then increased by 30% ☐ 40 increased by 30%, then decreased by 30%. ii 156 increased by 2%, then decreased by 2% ☐ 156 decreased by 2%, then increased by 2%

    • i = and ii =
    • i = and ii <
    • i > and ii <
    • i < and ii >
    Check

15. 15. Raj uses this method to work out 50 increased by 20%, then increased by 10%. Use Raj’s method to work out the final value after these compound percentage increases. i 60 increased by 30%, then increased by 10%. ii 200 increased by 25%, then increased by 45%.

    • i 85.8 and ii 362.5
    • i 85.8 and ii 340
    • i 84 and ii 362.5
    • i 84 and ii 340
    Check

16. 16. Mari uses this method to work out 50 increased by 20%, then increased by 10%. Use Mari’s method to work out the final value after these compound percentage increases. i 300 increased by 80%, then increased by 65%. ii 40 increased by 16%, then increased by 5%.

    • i 735 and ii 48.4
    • i 891 and ii 48.4
    • i 735 and ii 48.72
    • i 891 and ii 48.72
    Check

17. 17. Patsi works out the percentage increase of the price of a litre of petrol over two weeks. In the first week the price increased by 5%. In the second week it increased by 2%. Use Mari’s method to work out the multiplier for the compound percentage change.

    • 1.07
    • 1.071
    • 1.0071
    • 1.71
    Check

18. 18. Petrol costs $1.20 a litre. It rises by 5%, then by 2%. What is the new price, to the nearest cent?

    • $1.30
    • $1.27
    • $1.29
    • $1.28
    Check

19. 19. Raj uses this method to work out 50 decreased by 20%, then decreased by 10%: 50 × 0.8 × 0.9 = 36. Use Raj’s method to work out the final value after these compound percentage decreases. i 80 decreased by 40%, then decreased by 30%. ii 600 decreased by 75%, then decreased by 20%.

    • i 33.6 and ii 120
    • i 24 and ii 120
    • i 33.6 and ii 30
    • i 24 and ii 30
    Check

20. 20. Mari uses this method to work out 50 decreased by 20%, then decreased by 10%: 0.8 × 0.9 = 0.72, then 50 × 0.72 = 36. Use Mari’s method to work out the final value after these compound percentage decreases. i 200 decreased by 15%, then decreased by 25%. ii 90 decreased by 10%, then decreased by 5%.

    • i 120 and ii 76.5
    • i 120 and ii 76.95
    • i 127.5 and ii 76.5
    • i 127.5 and ii 76.95
    Check