When adding and subtracting decimals, remember to keep the decimal points in line in the question and the answer.
David is doing some DIY. He buys a length of wood.
He needs to cut two pieces of wood - one of length and one of length .
What is the total length of wood that David needs to cut?
So the total length of wood that David needs to cut is .
David originally had of wood. What is the length of the piece of wood that is left over?
You can add zeros after a decimal point without affecting its value, so is the same as .
David cut off , so we need to calculate
This means that there is of wood left over.