Number and Calculation
Number and Calculation is the ISEB Common Entrance topic covering the four operations with whole numbers and negative numbers, factors, multiples, primes, order of operations (BIDMAS) and rounding. It underpins every other 13+ Maths topic, since accurate non-calculator and calculator arithmetic is needed throughout the paper.
Before you start
No specific prerequisites - this is a good place to start.
Method
- Read the question carefully and decide whether a calculator is needed or whether a mental or written method is expected.
- For mixed operations, apply BIDMAS: brackets, indices, then division and multiplication (left to right), then addition and subtraction (left to right).
- For factors and multiples questions, systematically list factor pairs or use prime factorisation to find the HCF or LCM.
- For negative numbers, think of a number line: adding a negative is the same as subtracting, and subtracting a negative is the same as adding.
- Check rounding questions by identifying the correct place value and looking at the next digit to decide whether to round up or down.
- Always estimate your answer first, by rounding to 1 significant figure, so you can spot an unreasonable final answer.
Worked example
Calculate the value of 6 + 4 x (9 - 5) / 8, showing your method.
- Work out the bracket first: 9 - 5 = 4.
- Multiply and divide from left to right: 4 x 4 = 16, then 16 / 8 = 2.
- The expression now reads 6 + 2.
- Add to find the final value: 6 + 2 = 8.
Practice questions
Try each question, then tap to reveal the answer.
Exam-style questions
Written in the style of a 13+ Common Entrance exam paper, with a full mark scheme.
Work out (-9) + (-2) - (-7).
Express 90 as a product of its prime factors.
A youth club's trip costs 720 pounds in total, shared between the Year 7 group and the Year 8 group in the ratio 4 : 5. (a) Work out how much each group pays. (b) A late booking fee increases the Year 8 group's share by 10%. Work out the new amount the Year 8 group pays.
Free printable worksheet
Want more practice on paper? Download the number and calculation worksheet pack - 9 pages of exam-style questions with a full mark scheme. No sign-up, no email wall - just the PDF, free for personal and classroom use.
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