Mentally Multiply by 5, 25, 50, 250

This is a simple quicker math trick but it can be very useful for young students to solve seemingly difficult calculations. I will be glad to get your feedback on this.

Mental multiplication by 5, 25, 50, 250, 500 and so on.

Any number can be expressed in different ways. For example, 5 can be expressed as 10x(1/2).

Trick: Multiplication by 5

Step 1: Multiply the number by 10, i.e. simply place a zero after the number.

Step 2: Halve the resultant number.

Example 1:

5 × 136 = ten times of 136 i.e. 1360 should be divided by 2 = 1360/2 = 680

Example 2:

5 × 343, half of 3430 is 1715

Also check out, how to mentally multiply by 111?

Trick: Multiplication by 50, 500, 5000 and so on..

The above logic can also be applied to 50 which is half of 100 i.e. 1/2×100

Instead of multiplying the number by 10 we have to multiply by 100. So we have to place two zeroes after the number.

Example 1:

50 × 136 = hundred times of 136 i.e. 13600 should be divided by 2 = 13600/2 = 6800

Example 2:

50 × 647 = hundred times of 647 i.e. 64700 should be divided by 2 = 64700/2 = 32350

Same logic can be extended to numbers like 500, 5000 and so on.

Trick: Multiplication by 25

For multiplication by 25, we have to go one step further, 25=100 x (1/2) x (1/2)

Step 1: Multiply the number by 100, i.e. simply place two zeroes after the number.

Step 2: Halve the resultant number.

Step 3: Again halve the resultant number.

Example 1:

25 × 136 = hundred times of 136 i.e. 13600 should be divided by 2 = 13600/2 = 6800. Again halve this number, 6800/2 = 3400

Example 2:

25 × 343, half of 34300 is 17150. Again half of 17150 is 8575.

The above logic can also be extended to numbers like 250, 2500 and so on.

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Vineet Patawari

Hi, I'm Vineet Patawari. I fell in love with numbers after being scared of them for quite some time. Now, I'm here to make you feel comfortable with numbers and help you get rid of Math Phobia!

17 thoughts to “Mentally Multiply by 5, 25, 50, 250”

  1. thanks for all this
    * if u want to multiply 25 with any no just put double zero and devide by 4
    25*12 —–1200/4 = 300
    25*444 44400/4 =11100

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