In KS2 Maths children will come to understand decimal numbers. In Year Five children should know the place value of figures in decimal numbers to two places - tenths and hundredths - and also be capable of doing some adding and subtracting with decimals. They should also be confident when rounding decimal numbers up or down, and be familiar with sums involving decimal measurements such as metres/cm or £/pence.

Decimal numbers are those that are smaller than a unit and are written after a decimal point. Decimal numbers are an alternative way of writing fractions. A quarter of a pizza written as a fraction would be ^{1}⁄_{4}, but written as a decimal would be 0.25. 0.25 is a decimal with two places - the 2 represents 2 tenths and the 5 is 5 hundredths.

Can you tell the difference between tenths and hundredths? Can you round a number to two decimal places? See how well you understand decimal numbers by playing this quiz.

1.

Which is the largest?

0.35

0.05

0.03

0.3

2.

What does the digit 2 represent in 5.12?

2 tens

2 tenths

2 units

2 hundredths

In decimals the first column after the units is tenths and the second column is hundredths

3.

What is 8.5cm in mm?

8.5mm

85mm

850mm

8,500mm

There are 10mm in 1cm therefore we multiply by 10 to find the answer

4.

Which is the smallest of these numbers?

0.12

1.02

0.02

0.01

5.

Which is the decimal fraction equivalent to seven and forty two hundredths?

7.042

7.42

0.742

74.2

Forty two hundredths is equivalent to four tenths and two hundredths

6.

What is the figure 6 worth in 0.26?

6 hundredths

6 units

6 tenths

6 tens

Remember - tenths, hundredths, thoudandths

7.

How is 3.57 changed to 3.6?

Add 0.03

Subtract 0.3

Add 0.3

Subtract 0.03

Just like 357 + 3 = 360

3.57 + 0.03 = 3.6

3.57 + 0.03 = 3.6

8.

What is the next number in the following sequence? 0.24, 0.26, 0.28, 0.3

0.32

0.35

1.3

1.32

the numbers are going up by 0.02, or ^{2}⁄_{100} every time

9.

Which is a decimal fraction halfway between 2.1 and 2.2?

2.12

2.13

2.14

2.15

There are ten hundredths in a tenth so half of one tenth is 5 hundredths

10.

How is 0.07 changed to 0.02?

Add 0.5

Subtract 0.5

Subtract 0.05

Add 0.05

Just like 7 - 5 = 2

0.07 - 0.05 = 0.02

0.07 - 0.05 = 0.02

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^{35}⁄_{100}is larger than^{30}⁄_{100},^{5}⁄_{100}or^{3}⁄_{100}