Mental Arithmetic: Practice Set 8
This is the eighth timed practice set of 13+ Common Entrance Mental Arithmetic questions on the site, testing the same quick recall and rapid calculation skills as the core Mental Arithmetic topic, the four operations, fractions, percentages, ratio, rounding and simple algebra, worked out rapidly with little or no written working, as in the real timed test.
Before you start
Make sure you're comfortable with these topics first:
Method
- Keep your times tables up to 12 x 12, key fraction-percentage equivalents, and common squares up to 15^2 instantly available, since Mental Arithmetic questions are timed too tightly for working these out from scratch.
- Break down a calculation into smaller, easier steps in your head, for example finding 10% first and adjusting to find other percentages, rather than attempting the whole calculation in one go.
- Apply the correct order of operations for any multi-step calculation: brackets, indices, multiplication and division, then addition and subtraction.
- For money and measurement questions, keep track of the units at every stage and convert between them, such as pence to pounds, before combining amounts.
- For ratio and sharing questions, work out the value of one share first, then multiply up to find the amount each person or group receives.
- Practise against a timer regularly, since the pace of the real test, not the difficulty of any single question, is usually what makes Mental Arithmetic hard.
Worked example
A jumper costs 42 pounds. In a sale it is reduced by 30%. Calculate the sale price.
- Find 10% of 42 pounds: 42 / 10 = 4.2 pounds.
- Find 30% by multiplying the 10% value by 3: 4.2 x 3 = 12.6 pounds.
- Subtract the discount from the original price: 42 - 12.6 = 29.4 pounds.
- State the final answer: the sale price is 29.40 pounds.
Practice questions
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Q1Calculate 56 + 29.Show answer
Answer: 85
Q2Work out 8 x 6.Show answer
Answer: 48
Q3Find 10% of 95 pounds.Show answer
Answer: 9.50 pounds
Q4Work out 3 + 6 x 2 - 4.Show answer
Answer: 11 (multiply first: 6 x 2 = 12, then 3 + 12 - 4 = 11)
Q5108 pounds is shared between Amir and Bea in the ratio 4:5.Show answer
Answer: Amir gets 48 pounds and Bea gets 60 pounds (one part = 108 / 9 = 12, so 4 x 12 = 48 and 5 x 12 = 60)
Q6A tap fills a bucket at a constant rate of 3 litres every 2 minutes. Work out how many litres it fills in 10 minutes.Show answer
Answer: 15 litres (rate = 1.5 litres per minute, and 1.5 x 10 = 15)
Exam-style questions
Written in the style of a 13+ Common Entrance exam paper, with a full mark scheme.
Work out -8 - 5 + 12.
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Leo buys 3 pens at 1.25 pounds each and a notebook for 2.40 pounds. He pays with a 10 pound note. Calculate his change.
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Free printable worksheet
Want more practice on paper? Download the mental arithmetic: practice set 8 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 8 of 13+ Maths Workbook, the whole course as one free printable PDF.
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