Number
Decimals
Compare and order decimals, add and subtract them, and switch between decimals and fractions.
A decimal point does not start a new number — it just marks where the whole ones stop. Every place to the right of it is worth a tenth of the place before, so the first place counts tenths, the second hundredths and the third thousandths. That is the same pattern as the places to the left of the point, carried on downwards.
Zeros on the end are free
0.6 and 0.60 are worth exactly the same, because six tenths is sixty hundredths. That is what makes adding and subtracting decimals easy: give both numbers the same number of decimal places first, then line the points up and work as usual.
Have a play
Move between 3 and 4 in tenths. A whole line of numbers is hiding between two whole ones.
Tap anywhere on the line.
Worked example
Which is larger, 0.7 or 0.68?
Do not count digits — 0.68 is longer but that decides nothing.
This is the commonest mistake with decimals, and it comes from reading 68 as a whole number.
Try it together
Now let us work out 5.6 + 2.75 together.
One number has one decimal place and the other has two. Split the sum into whole ones and parts, and neither half is hard.
1.Deal with the whole ones first. What is 5 + 2?
Have a go
Have a go on your own: 4.5 - 1.25
Hint: Write 4.5 as 4.50 first.
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.