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Mathematics original practice and explained answers

You want questions that test your understanding, with answers that show every step rather than just a number.

On this page
  1. How to use the set
  2. Questions
  3. If you got these wrong
  4. When does practice need a teacher?

This page holds eleven original questions in rising difficulty, across number, algebra, geometry and data. Each answer is worked in full so you can compare your method, not just your result.

Attempt each question on paper first. Then open the answer and compare line by line. Every topic also has its own practice set inside its module, and the original mixed-practice builder can build a longer session.

How to use the set

  1. Work in a quiet block of 30 to 40 minutes.
  2. Write every step, even easy ones.
  3. Mark yourself honestly, then note the cause of each error: knowledge, interpretation or execution.
  4. Put each error in the mistake log.

Questions

Q1. Order from smallest to largest: −0.6, −2/3, −0.06, 1/2

Show answer

Convert: −2/3 ≈ −0.667 and 1/2 = 0.5. Negatives by distance from zero: −0.667 is furthest, then −0.6, then −0.06. Then the positive.

−2/3, −0.6, −0.06, 1/2

Q2. Work out 3/4 ÷ 2/5, giving an exact answer.

Show answer

Dividing by a fraction means multiplying by its reciprocal: 3/4 × 5/2 = 15/8.

15/8 (or 1 7/8)

Q3. Share RM 240 between Aina and Bala in the ratio 3 : 5.

Show answer

Total parts: 3 + 5 = 8. One part: 240 ÷ 8 = 30. Aina: 3 × 30 = 90. Bala: 5 × 30 = 150. Check: 90 + 150 = 240.

Aina RM 90, Bala RM 150

Q4. A bag costs RM 90 after a 20% increase. What was the price before the increase?

Show answer

After a 20% increase the price is 120% of the original, so original × 1.2 = 90. Original = 90 ÷ 1.2 = 75. Check: 75 × 1.2 = 90.

RM 75

Q5. A price of RM 50 rises by 40%, then the new price falls by 40%. Find the final price and the overall percentage change.

Show answer

Rise: 50 × 1.4 = 70. Fall: 70 × 0.6 = 42. Overall change: (42 − 50) ÷ 50 = −0.16.

RM 42, an overall decrease of 16%. The 40% fall is taken from a bigger base, so it removes more than the rise added.

Q6. Write 0.00072 in standard form.

Show answer

Move the decimal point until the number is between 1 and 10: 7.2. That took four places to the right, so the power is −4.

7.2 × 10⁻⁴

Q7. A length is 8.4 cm, correct to 1 decimal place. Write its lower and upper bounds.

Show answer

One decimal place means the rounding unit is 0.1, so the half-interval is 0.05.

Lower bound 8.4 − 0.05 = 8.35. Upper bound 8.4 + 0.05 = 8.45.

8.35 ≤ length < 8.45

Q8. Solve 3(x − 2) = 2x + 5.

Show answer

Expand: 3x − 6 = 2x + 5. Subtract 2x: x − 6 = 5. Add 6: x = 11.

Check: left side 3(11 − 2) = 27; right side 2(11) + 5 = 27.

x = 11

Q9. Solve the simultaneous equations 2x + y = 11 and x − y = 1.

Show answer

Add the equations to remove y: 3x = 12, so x = 4. Substitute into x − y = 1: 4 − y = 1, so y = 3.

Check in the first equation: 2(4) + 3 = 11.

x = 4, y = 3

Q10. A right-angled triangle has shorter sides 5 cm and 12 cm. Find the smaller acute angle, to 1 decimal place.

Show answer

The smaller angle is opposite the shorter side 5. The side 12 is adjacent. Use tan θ = opposite ÷ adjacent = 5/12.

θ = tan⁻¹(5/12) = 22.6° (to 1 d.p.).

Check: the hypotenuse is 13, and sin 22.6° = 5/13 ≈ 0.385, which matches.

22.6°

Q11. A car travels 150 km in 2 hours 30 minutes. Find its average speed in km/h.

Show answer

Convert the time to hours: 2 hours 30 minutes = 2.5 hours. Speed = distance ÷ time = 150 ÷ 2.5 = 60.

60 km/h

A common slip is writing 2.30 hours. Thirty minutes is half an hour, not 0.30 hours.

If you got these wrong

Route each error type to the lesson that repairs it.

QuestionIf it went wrongGo to
Q1Ordered negatives by their digitsOrder signed numbers
Q2Multiplied by the original fraction, or cancelled wronglyFractions without decimal rounding
Q3Divided by 2 or by 3 instead of 8Share in a ratio
Q4Took 20% off 90Reverse a percentage increase
Q5Said the changes cancelWhy rise and fall do not cancel
Q6Wrong sign or count of placesSmall measurements in standard form
Q7Used 0.1 instead of 0.05Recover an interval
Q8Sign error when expandingLinear equations with brackets
Q9Subtracted when signs needed addingSimultaneous relationships
Q10Used the wrong side pairRight-triangle trigonometry
Q11Treated minutes as a decimalRates, time and compound quantities

If you lost accuracy through early rounding, see the calculator accuracy help page. If you understood every step but could not start, see choosing a method.

When does practice need a teacher?

Some students read every answer here and still feel that the next question will go wrong in a new way. That is the point where listening to your reasoning helps more than another worksheet. In online one-to-one Mathematics tuition, a teacher can ask you to solve a problem aloud and notice where a sound idea turns into a wrong line.

For your route and scope, see the study route and revision page.

Questions people ask

Are these real exam questions?

No. Every question here is original and written to practise a skill, not to copy or predict an exam paper. For full papers, use official materials from Cambridge or your exam centre. Use this page to find and repair the skills that make papers difficult.

Should I use a calculator for these questions?

Try them without one first, since most use simple numbers. Then check with a calculator. Your actual calculator rules depend on your syllabus, paper and exam year, so read them on the Cambridge page for your code.

How do I use the answers without just copying them?

Attempt the question fully, write your answer, then open the worked solution and compare line by line. If you differ, find the first line where you differ and ask why. Redo the question the next day from a blank page.

What do I do after I finish?

Log every wrong answer with its cause, then repair the one or two most frequent. The mistake log keeps a retest queue so that a fresh question returns a few days later. A full mixed set can be built with the practice builder.

Sources

  1. Cambridge IGCSE Mathematics 0580 syllabus page

Updated:

Your next step

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