Quick Eleven Times (I)
The tricks for finding out quick answers for different multiplication problems are based on a very useful structural property of multiplication. It is the distributive property of multiplication. This property was explained earlier in short, in the articleThree rules simplify multiplication. Children should be taught this property at some stage while dealing with multiplication.
Let us examine how this property provides flexibility in discovering the correct answer for any multiplication fact. Many children are confused when asked, "What is eight times seven?" They feel that it is either 54 or 56. They do not recall the correct answer in time. This is the situation where children can use the distributive property of multiplication over addition and get to the correct answer. They have a choice of many ways to use this property. Some of these choices are shown in the figure below. We can teach this property in such a way that children discover it themselves. The teacher can use a following type of situation. Suppose there is a small theatre in the town. The theatre is partitioned lengthwise into two portions by a central passage. In the right portion of this theatre there are nine rows of chairs and in each row there are seven chairs. In the left portion of this theatre there are nine rows of chairs and in each row there are eight chairs. We want to know at a time, how many people could attend a show. Analysis of this problem is presented in the figure below. After understanding the practical value of the distributive property of multiplication over addition, children should be encouraged to find out easier ways of managing many multiplication problems like finding out eleven times any number.
The copyright of the article Quick Eleven Times (I) in Math for Kids is owned by Vidya Narayan Wadadekar . Permission to republish Quick Eleven Times (I) in print or online must be granted by the author in writing.
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