Quick Eight Times (III)

In the previous article we subtracted 3126 from 8347 twice, using one step procedure. You might have tried to write the straight forward steps which were interwoven in the procedure we actually followed. You may check the steps you have found with those I have provided below: .





If you go through all the steps given here and the one step procedure that we followed for subtracting twice the number from the given number, you will gain insight into the trick of getting eight times of any big number quickly.

Let us try to find eight times of 5689. As usual we will start by writing ten times 5689 that is 56890. From this we will be subtracting 5689 twice using the one step procedure discussed above. This subtraction will give us the product of eight times 5689.

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If you solve some more examples using the strategy shown above, you can find some more scope to make it still simpler.

Observe the first step in the example above. What we have done is subtracted the digit in the units place from ten and then doubled the remainder. Since the digit in the units place in the above example was 9, we subtracted it from 10. This gave us 1 as the remainder! This remainder we doubled. Thus we had 2 as the product. To this we added 0, which we got in the units place after getting ten times of the number 5689.

It means we will never have to add anything to the double of the first remainder! Thus, without even writing ten times of the number 5689 (i.e. the number which we want to multiply by eight) we can start straight away writing the digit in the unit's place of the answer. In the above example the two we get after doubling 1, is indeed the digit in the unit's place of the product eight times 5689.

Thus, we need to follow the three steps given below to get eight times of any number quickly:

Step 1: Start from the digit in the units place. Subtract the digit from ten and double the difference.

Step 2: Subtract the subsequent digits from nine and double the difference. To this product always add the right-side digit.

Step 3: Subtract 2 from the digit with highest place value in the answer.

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

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