Addition is an operation in which one number is added to another number. When adding a series of numbers, there are some strategies that help simplify the addition process. One thing to remember is to group numbers to make tens. For example, when adding 2 + 7 + 8, you can add the 2 and the eight first to get ten, and then add the seven to get 17. Some teachers call these groups of numbers that add to ten, "friendly tens," since they make adding easier for the student.
If a child is really confused about decimals, converting decimal numnbers into money is a great way to make things clearer. For example: a child may be asked to say how much bigger 1.3 is than 0.9. If they convert these decimals into money (£1.30 and 90p) they may find that they can do this calculation very quickly in their head, getting the answer 40p which they convert back into the decimal, 0.4. Demonstrating that money maths depends on decimal understanding is also an easy way to prove that decimals are actually useful in real life!