Mental Arithmetic: Practice Set 7
Mental Arithmetic: Practice Set 7 is a seventh timed set of 13+ Common Entrance mental arithmetic questions, continuing the quick-fire practice from Sets 1 to 6 across calculation, fractions, percentages, ratio, rounding and simple algebra.
Before you start
Make sure you're comfortable with these topics first:
Method
- Skim the whole question first to spot how many steps it needs, since Set 7 favours short multi-step problems over single calculations.
- Estimate the size of the final answer before calculating in detail, by rounding each number, so you can spot an error quickly.
- Use known equivalences between fractions, decimals and percentages to avoid a longer written calculation wherever possible.
- When a question mixes units (for example minutes and hours, or pence and pounds), convert everything to the smaller unit first, then convert the final answer back if needed.
- For a ratio question, always check which quantity the question is actually asking for before giving your final answer, since it is easy to give the wrong share.
- Keep calm under time pressure: if you cannot recall a fact instantly, work it out from a fact you do know, such as building 7 x 8 from 7 x 4 doubled.
Worked example
A meeting starts at 14:35 and lasts 1 hour 50 minutes. Work out the time the meeting ends.
- Add the hour first: 14:35 + 1 hour = 15:35.
- Add 25 of the remaining 50 minutes to reach a round number: 15:35 + 25 minutes = 16:00.
- Add the final 25 minutes: 16:00 + 25 minutes = 16:25.
- So the meeting ends at 16:25.
Practice questions
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Q1Work out 84 / 12.Show answer
Answer: 7
Q2Find 3/5 of 120.Show answer
Answer: 72
Q3Work out 60% of 45.Show answer
Answer: 27
Q4A train journey of 175 km takes 2.5 hours at a constant speed. Work out the speed in km/h.Show answer
Answer: 70 km/h (175 / 2.5 = 70)
Q5Simplify the ratio 32:12.Show answer
Answer: 8:3 (divide both parts by 4)
Q6Work out -15 + 4 x (-2).Show answer
Answer: -23 (multiply first: 4 x (-2) = -8, then -15 + (-8) = -23)
Exam-style questions
Written in the style of a 13+ Common Entrance exam paper, with a full mark scheme.
Work out 3^2 + 6^2.
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Ellis has 5.00 pounds. He buys 3 stickers at 60p each and a magazine for 2.15 pounds. Work out how much money he has left.
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A number is decreased by 30% to give 63. Work out the original number.
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Free printable worksheet
Want more practice on paper? Download the mental arithmetic: practice set 7 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 7 of 13+ Maths Workbook, the whole course as one free printable PDF.
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