Can your young mathematician add and subtract hundredths and thousandths less than 1 with regrouping? That's exactly what they do here. Students understand that when adding or subtracting decimals, it is important to align the decimal points and use zeros as placeholders. In this worksheet, they also need to regroup numbers to get the result. In this worksheet, numbers are laid one on top of another (vertical format). This encourages students to use the inherent place value structure to solve the problems.