These are about as hard as you will get for mental arithmetic. Many children (and adults) will find them very tricky!

Tricky sums, these. Think about the digits in the tenths and hundredths columns when working out these addition of decimals questions.

Using the standard written method to add thousands. All questions should be answered in this way. Take particular care that the units are lined up when adding these totals together.

Mental addition skills with numbers up to 3 decimal places.