Go Forth and Multiply
Here’s a quick test: Without using a pencil and paper, what are 8×8, 5×9, and 7×6? Mental math, especially with multiplication, can be tricky for many kids (and adults).While memorization of the times tables is the ideal once students understand what they mean, memories aren’t always reliable. So what can you do?
The good news is that there are many different tricks people use to help remember (or figure out) the answers to various multiplication questions. Below are a few to help with your times tables from 0x0 to 10 times any number.
Zero. Think, “It’s always zero.” Any number times zero is always equal to zero. Want to see a child smile? Start them with low numbers like 2×0, or 5×0, then ask them “A million times zero.”
Ones. Think, “It’s the same.” One times a number is always that number. E.g. If you only have one group of 5, the total has to be 5.
Twos. Think “Doubles.” Some kids freeze if you ask them “two times” something, but answer quickly if you ask them to tell you what that number is when doubled.
Threes. Think “Doubles + one more group.” The great thing about multiplication is that you can break problems apart to get the answer. Look at 3×5. If children know two groups of five is ten (2×5=10), simply have them add one more group of five to get 15.
Fours. Think “Double, double.” (Coffee drinkers often like this one.) Double the answer, then double it again. Don’t know 4×8 but know 2×8? Then take 16 (2×8) and double it, and you get 32.
Fives. Think “Half of 10.” Most kids quickly figure out their tens times tables. Since five is half of ten, have them figure out what ten times the number is, and then half it. E.g. 5×8? Think 10×80 (80) divided by 2, which gives you 40.
Sixes. Think “Triple, double.” Triple the number, then double that answer.
Sevens. This one is the hardest to come up with a strategy that works for most people. You could think “Six times + one more group” or think “Five times plus two times a number.” But in many cases simply reversing the digits can be most helpful (E.g. 7×5 become 5×7).
Eights. Think “Double three times.” Because 2x2x2=8, doubling a number three times in a row gives you the same answer as eight times the number. Need 8×8? Double it (16). Double that answer (32). Then double that answer (64).
Nines. Think “10 times – one group.” E.g. 9×8 is like (10×8)-8. Simple and effective.
Tens. Think “Add a zero.” Multiply any number by ten, and all the existing numbers shift to the left and a zero is added to the right.
Help your child realize that the two numbers can be multiplied in either order. Don’t remember 8×5? What about the reverse: 5×8? And of course there is always “skip counting.” In the last example count by fives eight times, or eights five times.
So there you have it – some quick and easy strategies that may help your son or daughter get a little quicker at their mental math.
Rob Stringer, BA, Bed, CPC is an educator and International Parenting & Youth Coach. Visit www.YouthCoachCanada.com or call 905-515-9822.