Solve these multiplications:

1. 400 X 25?

2. 40 X 50?

3. 60 X 50?

4. 120 X 250?

5. 24 X 25?

How much time do you need to solve the above multiplications?

If you do it the traditional way, you will take about a minute or so. Let's observe the numbers carefully. The multiplier in all the cases is a multiple of 25. 

Let's look at the first calculation:

400 X 25

25 is nothing by 100/4. So multiplying a number with 25 is nothing but multiplying the number by 100 and dividing by 4. Multiplying a number by 100 is nothing but adding two zeroes at the right. Now 400 X 25 is nothing but 400 multiplied by 100 divided by 4.

It is nothing, but 40,000 divided by 4. The answer is therefore 10,000. It hardly takes a few seconds to do this calculation.


Let's look at second calculation:

40 X 50

50 is nothing but 100 divided by 2. The calculation therefore can be simplified as 40 multiplied by 100, divided by 2. the answer is 4,000 divided by 2 which is equal to 2,000. You can alternatively first divide the number by 2 and then multiply the result with 100. It is completely upto you.

Similarly, multiplication with 250 is nothing but multiplication with 1,000 followed by division with 4. You can alternatively divide the number with 4 and then multiply the result with 1,000

Here are some other simplifications:

Multiplication with 125 is nothing but division with 8 followed by multiplication with 1,000

Now try the following:

1. 240 X 125

2. 360 X 250

3. 160 X 25

4. 180 X 50

5. 200 X 500

6. 80 X 125


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