Use everyday activities to strengthen mental math skills
You can help your child hone his estimating and mental math skills by bringing him grocery shopping with you and having him keep a running total of the appropriately rounded-up-or-down prices. You can keep track too and after you check out, you can compare your answers with the actual total and see who came closer. For an added challenge, have him try to find the best per-unit price on items that come in a variety of sizes. Sometimes bigger is NOT better!