KS2 Maths · Topic guide

Decimals and Percentages (Year 5)

Decimals and Percentages (Year 5) introduces the percent symbol as meaning 'out of 100', and teaches pupils to convert between simple fractions, decimals and percentages, such as 1/2, 0.5 and 50%, as well as to find simple percentages of whole number amounts.

Year 3-6 (KS2)FractionsNational CurriculumKS2 SATs

Before you start

Make sure you're comfortable with these topics first:

Method

  1. Understand that 'per cent' means 'out of 100', so 100% is the whole amount and 50% is exactly half of it.
  2. Learn the common equivalences by heart: 1/2 = 0.5 = 50%, 1/4 = 0.25 = 25%, 1/10 = 0.1 = 10%, and 3/4 = 0.75 = 75%, so these do not need to be worked out from scratch every time.
  3. To convert a decimal with tenths or hundredths into a percentage, multiply by 100, which moves the decimal point two places to the right.
  4. To convert a percentage into a decimal, divide by 100, which moves the decimal point two places to the left.
  5. To find 10% of an amount, divide the amount by 10; use this to build up to other percentages, such as finding 20% by doubling 10%, or 5% by halving 10%.
  6. To find 50% or 25% of an amount, use fraction knowledge instead: 50% means dividing by 2, and 25% means dividing by 4.
  7. Check a percentage answer is sensible by comparing it with 50% (half) of the amount, since a mistaken calculation often gives an answer bigger than the whole amount itself.

Worked example

A school has 40 pupils in Year 5. 25% of them walk to school. How many pupils walk to school?

  1. Recognise that finding 25% is the same as finding a quarter of the amount, since 25% = 1/4.
  2. Divide the total number of pupils by 4: 40 divided by 4 = 10.
  3. Check the answer makes sense: half of 40 is 20, and 10 is half of that, so 10 is a sensible size for a quarter.
  4. So 10 pupils walk to school.

Practice questions

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Q1Write 0.6 as a percentage.Show answer

Answer: 60%

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Q2Write 40% as a decimal.Show answer

Answer: 0.4

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Q3Find 10% of 90.Show answer

Answer: 9

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Q4Find 50% of 36.Show answer

Answer: 18

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Q5Write 3/10 as a decimal and as a percentage.Show answer

Answer: 0.3 and 30%

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Q6Find 25% of 200.Show answer

Answer: 50

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Exam-style questions

Written in the style of a KS2 Maths exam paper, with a full mark scheme.

Q1[2 marks]

Write 7/10 as a decimal and as a percentage.

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Q2[2 marks]

A shop has 60 toys. 20% of them are dolls. How many dolls are there?

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Q3[2 marks]

Ahmed says that 0.08 is the same as 80%. Explain why Ahmed is wrong, and write the correct percentage for 0.08.

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Free printable worksheet

Want more practice on paper? Download the decimals and percentages (year 5) worksheet pack - 6 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.

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