13+ Common Entrance · Topic guide

Mental Arithmetic: Practice Set 6

Mental Arithmetic: Practice Set 6 is a sixth timed set of 13+ Common Entrance mental arithmetic questions, giving further quick recall and rapid calculation practice across the four operations, fractions, percentages, ratio and simple algebra.

Year 7-8 (13+)MathsISEB

Before you start

Make sure you're comfortable with these topics first:

Method

  1. Practise mixed operations in one calculation, applying the correct order (brackets, indices, multiplication/division, addition/subtraction) automatically rather than working left to right.
  2. Check an answer using the inverse operation, for example checking a subtraction by adding the answer back to the number subtracted.
  3. Use known times tables to find related division facts instantly, for example knowing 7 x 8 = 56 also gives 56 / 8 = 7.
  4. For fraction and percentage questions, pick whichever form is quickest to work with for the numbers given, converting only if it makes the calculation easier.
  5. Keep track of units through a calculation involving money, length or time, converting once at the start rather than partway through.
  6. If a question feels slow to answer, try breaking the numbers apart differently, for example splitting 19 into 20 - 1 before multiplying.

Worked example

Work out 19 x 6 using a quick mental method.

  1. Rewrite 19 as 20 - 1, since 20 is easier to multiply by.
  2. Multiply 20 by 6: 20 x 6 = 120.
  3. Multiply 1 by 6: 1 x 6 = 6.
  4. Subtract the second result from the first: 120 - 6 = 114.

Practice questions

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Q1Work out 56 / 7.Show answer

Answer: 8

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Q2Find 2/9 of 63.Show answer

Answer: 14

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Q3Work out (4 + 3) x (9 - 5).Show answer

Answer: 28

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Q4A jacket costs 65 pounds. Work out the cost after a 20% discount.Show answer

Answer: 52 pounds (65 x 0.8 = 52)

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Q5Write 5:20 as a ratio in its simplest form.Show answer

Answer: 1:4

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Q6Work out -12 + 4 x 3.Show answer

Answer: 0 (multiply first: 4 x 3 = 12, then -12 + 12 = 0)

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Exam-style questions

Written in the style of a 13+ Common Entrance exam paper, with a full mark scheme.

Q1[2 marks]

Work out 4 x 5^2.

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Q2[3 marks]

A cafe orders 8 boxes of teabags, each containing 40 teabags, at a cost of 90p per box. Work out (a) the total number of teabags ordered, and (b) the total cost.

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Q3[4 marks]

A number is trebled, then 8 is added, giving 41. Work out the original number.

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Free printable worksheet

Want more practice on paper? Download the mental arithmetic: practice set 6 worksheet pack - 13 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.

This topic is chapter 6 of 13+ Maths Workbook, the whole course as one free printable PDF.

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