Give the kid the "trick" and give yourself a calculator. Race to see who gets the answer first. (Let them win!)
At a restaurant, ask them to mentally calculate the 10% or 20% tip before you look at the receipt.
This is arguably the coolest-looking trick in mental math. It works for any two-digit number multiplied by 11. Mental Math Kids Can't Resist!: Tips, Short-cut...
Most kids struggle with numbers that require "carrying" or "borrowing." Friendly numbers make those problems disappear.
This is a lifesaver for multiplication tables that haven't been memorized yet. It simplifies complex problems into manageable ones. Give the kid the "trick" and give yourself a calculator
Take the first digit and multiply it by the "next" number up. 65 x 65 The end is 25 . The first digit is 6. The next number up is 7. Put them together: 4,225 . How to Make it "Irresistible"
If the middle sum is 10 or more (like 87 x 11), just carry the "1" to the first digit! 3. The "Doubling and Halving" Method This is arguably the coolest-looking trick in mental math
Round one number to the nearest ten to make it "friendly," solve the problem, and then adjust. Example: For 38 + 25 , turn 38 into 40 (by adding 2). The Math: . Now, take away that extra 2 you added earlier.