Why does my child think 2.5 + 0.75 = 1.00?
Your child lines up the last digits instead of the decimal points, such as 2.5 + 0.75 = 1.00.
Why children do it
With whole numbers, lining up the last digits always works, because the last digit is always the ones. Decimals can have different numbers of digits after the point, so lining up the ends puts tenths under hundredths. Lining up the decimal points keeps every digit in its place: 2.50 + 0.75 = 3.25.
How to help at home
Write the numbers under each other with the decimal points in a line, filling any gaps with 0.
The right way
Calculate: 2.2 + 0.72
- 2.20 + 0.72Line up the points: 2.2 is the same as 2.20.
- 2.92Add, keeping the point in line.
Find out where your child is
A free maths check, in about 15 minutes, shows what your child knows and the mistakes they make. No sign-up.
Start the free check