Multiplication facts can be mastered by relating new facts to already existing knowledge. While it is generally agreed that children should be given the opportunity to find their own methods of learning the facts, there are several strategies that could be introduced. They include:
- Doubles: Multiplication by two should not prove to be a great problem to students who know their addition facts.
- Fives Facts: Students should become familiar with counting by fives; thus, multiplying a number by 5 should be related to this counting by fives.
- Zeros and Ones: Children should be given the opportunity to find their own reasoning as to why a number multiplied by zero is equal to zero and that a number multiplied by one is equal to that number. They should not be explicitly told these rules but should be able to explain why this is so. Upon gaining this knowledge, they will know 36 facts of single-digit multiplication.
- Nifty Nines: The nines facts are among the easiest set to remember and they are often fun patterns to find. "Two of these patterns are useful for mastering the nines: (1) The tens digit of the product is always one less than the "other" factor that is not 9, and (2) the sum of the two digits in the product is always 9" (Van de Walle and Folk 151). Upon adding these two facts together, one will get the product of the two numbers. Another strategy which many children find both interesting and very helpful is one in which you use ten fingers to find the product. For example, your fingers are numbered 1-10 starting with your thumb on your left hand. You put down the finger representing the number you are multiplying by 9. Then, the number of fingers standing on the left of that finger represents the number of tens in the product and the number of fingers to the right represent the ones of the product. A diagram of this strategy can be found at http://www.multiplication.com/teachold/teach11o.htm.
These strategies are successful in helping students learn 75 of the possible 100 multiplication facts for single-digit multiplication! (Van de Walle and Folk 149).
To help with the 25 remaining facts, students can use the facts they already know along with mental addition. For example, the 4's can be learned by doing doubles and doubles again and the 3's can be learned by using doubles and adding on one extra set. (Van de Walle and Folk 152).
Van de Walle, John, and Folk, Sandra. Elementary and Middle School Mathematics - Teaching Developmentally. Canadian ed. Pearson Education Canada, 2005.