Painless Nine Times (III)


By now you must have mastered the procedure of telling nine times of some numbers on your fingers. However, you must have worried about remembering some of the nine times, listed in the table to your left-hand side. We were not able to show them by bending a finger. The reason was that the digits in these products when added gave sums more than nine.

In the present article I will show you another method of finding nine times of any number quickly and accurately. For this purpose let us review the nine times of numbers from 1 to 10 with a different perspective.

In the table below you can see how we can get the product by simple multiplication followed by subtraction. For example, we want to know the answer for nine times eight.

Here is the way to get it. First, multiply eight by ten. We get eighty. Next, from eighty we subtract the number eight (i.e. the number of which nine times we want to find). Thus, eighty minus eight is equal to eighty-one. In other words, nine times eighty is eighty-one.

Now let us check if it works for nine times of any number more than ten. Suppose, we take the number fifteen, whose nine times we are interested in. Let us follow the two steps mentioned in the paragraph above. First, we will multiply fifteen by ten. That gives one hundred fifty. See example 1 of the figure here. Next, from one hundred fifty we will subtract fifteen. Thus, 150 - 15 is equal to 135. This is indeed the right answer!

Let us now take a number more than a hundred. Let it be two hundred thirty-eight! First, we will multiply two hundred thirty-eight by ten. That will give the product two thousand three hundred eighty. Take a look at the example 2 of the figure here. Next, we subtract two hundred thirty-eighty from two thousand three hundred and eighty. Thus, 2380 - 238 is equal to 2142. By using the usual method of multiplication also we get the same answer!

Thus, we can generalize our observation for finding nine times of any number as given below:

Nine times of any number = ten times the number - the number.

The difficult part in this method is only that of subtraction. If you can subtract mentally and accurately isn't this a simple way of getting nine times easily?

See if you can get answers for the following problems by using the above method.

The copyright of the article Painless Nine Times (III) in Math for Kids is owned by Vidya Narayan Wadadekar . Permission to republish Painless Nine Times (III) in print or online must be granted by the author in writing.

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