Today's blog is about tricks to help your child master multiplication facts. Below are the tricks I teach. Some may seem obvious to us (and even to most children), but
each year, I encounter children who are surprised to learn some of
2's If you know your addition doubles facts, you can quickly do 2's.
(Ex: 2x7= 7+7 (or 2 sevens added together) =14)
3's The distributive property teaches us that if we know 2x7 and 1x7, then we know 3x7. (2x7 =14
so use the doubles fact and add 7 more.
4's Again, the distributive property says we can double (x2) and double again to learn our 4's.
(EX: 7x4= 7x2=(14) x2 again =28)
5's While most kids think that counting by 5's on their fingers is the quickest way to do 5's, thinking of the numbers on the clock is the fastest way to learn them. Most kids know that the 3 represents 15, 6 is 30, and 9 is 45 on the clock, and it doesn't take long to fill in the others with a minimum of practice.
Like doubling the 2's to learn 4's, kids can double 3's
to find 6's. (Ex: 6x7 is the same as 3x7 (21) doubled, which yields 42.)
Another trick I teach for 6's is to take the 5 fact and add one more set of the number. (Ex: 6x7 is 5x7 (35) +1 more set of 7 to make 6 groups of 7 or 42)
7's By the time kids get to 7's, they know all of the
7 facts except 7x7. 8x7, and 9x7. Since they willl
soon have a trick for both 8's and 9's, the only one they will struggle with is 7x7. At this point, I would work with my child to memorize all the mutliplicaiton doubles (called square
8's Like 4, 8 is a power of 2, so we take the 4 rule and go one more step; double, double agian, and double once more (or double the 4 fact if they have mastered it). Like 7, kids should already have all the 8's up to 8x8 and 9x9.
9's There are so many tricks with 9's! 3 of my favorites are the finger trick (hold up all 10 fingers. Lower the finger corresponding to the number you are multiplying by your 9. All the fingers to the left represent the ten's place, the ones
on the right represent the one's place (the digits in all multiples of 9 add up to 9 or a mutliple of nine).
The second works on the same premise as the first: subtract 1 from 9's partner to get the ten's place, the remainder from 9
is the one's digit (Ex: 7x9: take one from 7 to get 6 in the ten's place. You need three more to make 9, so 3 is your one's digit.)
The third is using the distributive property (Ten 7's are 70, so 9 sevens would be 70-7, or 63.)
Of course, these are only crutches to help your child until he/she masters the facts by rote. The homework I have assigned and the games/computer activities/videos we do in class are all designed to master facts through repetition of auditory and visual stimuli. Encourage your child to do MathMagic at least 5 minutes each night and you will see a tremendous difference in their multiplicaiton skills. Don't forget to celebrate with them by showing joy with a high-five or a pat on the back when they master a new set. I have yet to meet the 4th grader who isn't elated to pass each level as though they mastered a new level on Mario Brothers!