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Primary Maths · Year 4Chapter 6 · Decimals and money
Year 4 · Tenths, Hundredths and Money · Lesson 6.3

Year 4: Halves, quarters and three quarters

Part of the Year 4 tenths, hundredths and money chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)

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6.3

Halves, quarters and three quarters

Year 4
Decimal equivalents of 1/2, 1/4 and 3/4, Simple measures with decimals

Some fractions are used so often that it is worth knowing them as decimals. Use a hundred square. It has 100 small squares, and each one is 0.01.


1/4 = 0.25

1/2 = 0.5

3/4 = 0.75
A quarter, a half and three quarters of a hundred square.

Why is a half 0.5 and also 0.50? A half is 5 tenths, 0.5. It is also 50 hundredths, 0.50. A 0 on the end of a decimal does not change the number, so 0.5 = 0.50.

00.250.500.751ABC
On the number line from 0 to 1: A = 1/4 = 0.25, B = 1/2 = 0.5 and C = 3/4 = 0.75.

Going the other way. To write 0.75 as a fraction, write it as hundredths: 75/100. Then divide the top and the bottom by 25: 75 ÷ 25 = 3 and 100 ÷ 25 = 4. So 0.75 = 3/4.

Money. There are 100p in £1. So a half of £1 is 50p = £0.50, a quarter of £1 is 25p = £0.25, and three quarters of £1 is 75p = £0.75.

50p20p5p
50p + 20p + 5p = 75p = £0.75, which is three quarters of £1.

Measures. We use these decimals for lengths, masses and capacities. 2.5 m is 2 and a half metres. 1.75 kg is 1 and three quarters of a kilogram. 0.25 litres is a quarter of a litre.

11.251.501.752A
A parcel has a mass of 1.75 kg. That is 1 and 3/4 kg.

Key words. A hundred square has 100 small squares. A half is 1 of 2 equal parts and a quarter is 1 of 4 equal parts.

Key ideas

  • 1/2 = 0.5 (also 0.50 and 5/10).
  • 1/4 = 0.25 (25 hundredths).
  • 3/4 = 0.75 (75 hundredths).
  • A half of £1 is 50p = £0.50. A quarter is 25p. Three quarters is 75p.
  • With a whole number: 2 1/2 = 2.5, 3 3/4 = 3.75.
  • A decimal like 0.5 does not change if you add a 0 on the end: 0.5 = 0.50.
Worked example 6.3.1
Write 1/4 as a decimal.

Key words. A hundred square has 100 small squares. Each small square is 1 hundredth. A half is 1 of 2 equal parts and a quarter is 1 of 4 equal parts.

Method. Use a hundred square. Cut it into equal parts to find how many hundredths the fraction is worth. Then write it as a decimal.

  1. Think of a hundred square. It has 100 small squares, and each is 1 hundredth. Cut it into 4 equal parts.
    100 ÷ 4 = 25 squares in each part
  2. Find how many squares are in 14. 1 part of 25 squares.
    1 part = 25 squares
  3. Write it as hundredths. The bottom number is 100 because the square has 100 squares.
    14 = 25100
  4. Write it as a decimal. 25 hundredths is 0 ones, 2 tenths and 5 hundredths.
    25100 = 0.25

Check. 25 × 4 = 100, so 4 equal parts of 25 squares fill the whole hundred square. Known facts: 1/2 = 0.5, 1/4 = 0.25, 3/4 = 0.75. ✓

Watch out. 1/4 is 0.25, not 0.4 and not 0.14. A quarter is 25 hundredths.

Worked example 6.3.2
Write 3/4 as a decimal.

Key words. A hundred square has 100 small squares. Each small square is 1 hundredth. A half is 1 of 2 equal parts and a quarter is 1 of 4 equal parts.

Method. Use a hundred square. Cut it into equal parts to find how many hundredths the fraction is worth. Then write it as a decimal.

  1. Think of a hundred square. It has 100 small squares, and each is 1 hundredth. Cut it into 4 equal parts.
    100 ÷ 4 = 25 squares in each part
  2. Find how many squares are in 34. 3 parts of 25 squares.
    3 × 25 = 75 squares
  3. Write it as hundredths. The bottom number is 100 because the square has 100 squares.
    34 = 75100
  4. Write it as a decimal. 75 hundredths is 0 ones, 7 tenths and 5 hundredths.
    75100 = 0.75

Check. 25 × 4 = 100, so 4 equal parts of 25 squares fill the whole hundred square. Known facts: 1/2 = 0.5, 1/4 = 0.25, 3/4 = 0.75. ✓

Watch out. 1/4 is 0.25, not 0.4 and not 0.14. A quarter is 25 hundredths.

Worked example 6.3.3
Write 0.75 as a fraction in its simplest form.

Key words. A hundred square has 100 small squares. Each small square is 1 hundredth. A half is 1 of 2 equal parts and a quarter is 1 of 4 equal parts.

Method. Write the decimal as hundredths. Then divide the top and the bottom by the same number to make it simpler.

  1. Write the part after the point as hundredths. Two digits after the point mean the bottom number is 100. If there is only one digit, write a 0 after it first: 0.5 = 0.50.
    75 hundredths = 75100
  2. Find a number that divides into the top and the bottom. The biggest one makes the fraction as simple as possible.
    75 and 100 both divide by 25.
  3. Divide the top and the bottom by it. Dividing both by the same number does not change the value.
    75 ÷ 25 = 3 and 100 ÷ 25 = 4
    75100 = 34
  4. Write the fraction.
    0.75 = 34

Check. Go back to a decimal: 34 of 100 is 75, which is 75 hundredths = 0.75. ✓

Watch out. Do not forget to simplify: 0.75 is 3/4, and 75/100 is the same amount written in a longer way.

Worked example 6.3.4
Write 0.5 as a fraction in its simplest form.

Key words. A hundred square has 100 small squares. Each small square is 1 hundredth. A half is 1 of 2 equal parts and a quarter is 1 of 4 equal parts.

Method. Write the decimal as hundredths. Then divide the top and the bottom by the same number to make it simpler.

  1. Write the part after the point as hundredths. Two digits after the point mean the bottom number is 100. If there is only one digit, write a 0 after it first: 0.5 = 0.50.
    50 hundredths = 50100
  2. Find a number that divides into the top and the bottom. The biggest one makes the fraction as simple as possible.
    50 and 100 both divide by 50.
  3. Divide the top and the bottom by it. Dividing both by the same number does not change the value.
    50 ÷ 50 = 1 and 100 ÷ 50 = 2
    50100 = 12
  4. Write the fraction.
    0.5 = 12

Check. Go back to a decimal: 12 of 100 is 50, which is 50 hundredths = 0.50. ✓

Watch out. Do not forget to simplify: 0.75 is 3/4, and 75/100 is the same amount written in a longer way.

Worked example 6.3.5
Write 2 1/4 as a decimal.

Key words. A hundred square has 100 small squares. Each small square is 1 hundredth. A half is 1 of 2 equal parts and a quarter is 1 of 4 equal parts.

Method. Use a hundred square. Cut it into equal parts to find how many hundredths the fraction is worth. Then write it as a decimal.

  1. Think of a hundred square. It has 100 small squares, and each is 1 hundredth. Cut it into 4 equal parts.
    100 ÷ 4 = 25 squares in each part
  2. Find how many squares are in 14. 1 part of 25 squares.
    1 part = 25 squares
  3. Write it as hundredths. The bottom number is 100 because the square has 100 squares.
    14 = 25100
  4. Write it as a decimal. 25 hundredths is 0 ones, 2 tenths and 5 hundredths.
    25100 = 0.25
  5. Add the whole number. The whole number goes in front of the point.
    2 + 0.25 = 2.25

Check. 25 × 4 = 100, so 4 equal parts of 25 squares fill the whole hundred square. Known facts: 1/2 = 0.5, 1/4 = 0.25, 3/4 = 0.75. ✓

Watch out. 1/4 is 0.25, not 0.4 and not 0.14. A quarter is 25 hundredths.

Worked example 6.3.6
A parcel has a mass of 1.75 kg. Write 1.75 as a mixed number.

Key words. A hundred square has 100 small squares. Each small square is 1 hundredth. A half is 1 of 2 equal parts and a quarter is 1 of 4 equal parts.

Method. Write the decimal as hundredths. Then divide the top and the bottom by the same number to make it simpler.

  1. Write the part after the point as hundredths. Two digits after the point mean the bottom number is 100. If there is only one digit, write a 0 after it first: 0.5 = 0.50.
    75 hundredths = 75100
  2. Find a number that divides into the top and the bottom. The biggest one makes the fraction as simple as possible.
    75 and 100 both divide by 25.
  3. Divide the top and the bottom by it. Dividing both by the same number does not change the value.
    75 ÷ 25 = 3 and 100 ÷ 25 = 4
    75100 = 34
  4. Put the whole number in front.
    1 and 34 = 134
  5. Write the fraction.
    1.75 = 134

Check. Go back to a decimal: 34 of 100 is 75, which is 75 hundredths = 0.75. ✓

Watch out. Do not forget to simplify: 0.75 is 3/4, and 75/100 is the same amount written in a longer way.

Worked example 6.3.7
Work out 3/4 of £2. Give your answer in pounds.

Key words. Pence (p) are small amounts of money. 100 pence make 1 pound.

Method. Change the money into pence. Find a fraction of it: divide by the bottom number, then multiply by the top number. Change back to pounds.

  1. Change the pounds into pence. 1 pound is 100 pence, so we can divide the pence exactly.
    £2 = 2 × 100 = 200p
  2. Find one part: divide by the bottom number, 4. The bottom number says how many equal parts.
    200p ÷ 4 = 50p
  3. Multiply by the top number, 3. The top number says how many parts we take.
    50p × 3 = 150p
  4. Change back to pounds and pence. 100p = £1, so divide by 100. Always show two decimal places.
    150p = £1.50

Check. 50p × 4 = 200p, so 4 parts make the whole amount. ✓

Watch out. Write money with two decimal places: £3.50, not £3.5.

Watch out

1/4 is 0.25, not 0.4 or 0.14. A quarter is 25 hundredths. And 0.5 is not the same as 0.05: 0.5 is a half but 0.05 is only 5 hundredths. Do not forget: 3/4 is 0.75, so it is MORE than a half.

Exercise 6C  Halves, quarters and three quarters

Non-calculator
1
FThe hundred squares are shaded. Write the decimal that is shaded.
(a)
Decimal =
(b)
Decimal =
(c)
Decimal =
2
FQuick-fire! Write each fraction as a decimal.
(a)12 =
(b)34 =
(c)14 =
(d)24 =
(e)510 =
(f)25100 =
3
FWrite each decimal as a fraction. Give each answer in its simplest form.
(a)0.5 =
(b)0.25 =
(c)0.75 =
(d)0.1 =
(e)0.01 =
(f)0.50 =
4
FWrite each mixed number as a decimal.
(a)212 =
(b)334 =
(c)114 =
(d)612 =
5
FWrite each decimal as a mixed number.
(a)2.5 =
(b)4.75 =
(c)1.25 =
(d)7.5 =
(e)3.25 =
6
FThe number line goes from 0 to 1. Write each point as a decimal.
01ABC
(a)A =
(b)B =
(c)C =
7
FWrite each measure as a decimal.
(a)12 m =
(b)34 kg =
(c)114 litres =
(d)212 km =
8
FWork out each fraction of the money. Give your answers in pounds.
(a)12 of £1 =
(b)14 of £2 =
(c)34 of £4 =
(d)12 of £5 =
9
PSPriya pours 1 litre of juice into 4 equal glasses.
1 litre
(a)What fraction of a litre is in each glass? Write it as a decimal.
(b)She drinks 3 of the glasses. What decimal of a litre is that?
10
PSA rope is 2 3/4 m long. Zara cuts off 1 m.
(a)Write the length of the rope as a decimal.
(b)How long is the rope now? Give your answer as a decimal.
11
RTom says, “14 = 0.4, because there is a 4 on the bottom.” Is Tom right? Explain.
12
RMatch each fraction to its decimal.   A 12   B 34   C 14   D 110
Decimals:   0.1    0.25    0.5    0.75
13
RWhich is the odd one out?   0.5    510    12    0.05.   Explain.
14
RI am a fraction with 4 on the bottom. I am more than 0.5 and less than 1. What fraction am I? Write me as a decimal too.

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