Properties of Multiplication

• Why should I bother learning this?

This is an excellent opportunity to provide examples of how the use of multiplication saves so much time compared to repeated addition. Using rolls of coins can be a motivating factor for many students. For example, bring in 10 rolls of nickels. Explain to the students that each roll contains 40 nickels. If a nickel is worth 5 cents, how many cents is a roll of nickels worth? Have a volunteer add 5 forty times at the board. Have another student multiply 5 x 40. The efficiency of using multiplication to find the total amount in equal groups will be evident.

• Why does zero times another number equal zero?

To explain multiplication by zero, be sure to reinforce that multiplication involves groups of items (for example, 2 x 5 is two groups of five). The expression 0 x 5 is zero groups of five. If you have zero groups then your product must be zero. Similarly, 5 x 0 is five groups with zero in each group. If there is zero in each group, then the product must be zero.

• Do you always get the same answer in a multiplication problem if you switch the numbers around like 4 x 7 and 7 x 4?

This is an excellent chance to discuss the commutative property of multiplication. Display a multiplication table in the classroom. Have students use the table to see how the commutative property works for multiplication.