How to Square A Number With Last Digit 5?

In my last post I have shown how to multiply with two numbers without using calculator. This is bit advanced post where I will show to make a square a number having five at last without using a calculator.

Say I have to square 15 that is 15X15=225

How to derive this my using simple calculation:

Step-1

Divide the numbers in the below written manner:

Step-2

Draw a line just after 5

Step-3

Multiply 5*5=25 and write it to the right of the bar

Step-4

Now add one to the top number here it is 1 so top number becomes 1+1=2

Step-5

Multiply 2*1(that is the left hand side ..this can be done again with multiply two number method)

Hence the result has come to 225.

Now let us try with a big number called 95X95

As per Step-1 and 2 this will look like-

Step-3

Following step -3 we will get 5*5=25

Step-4

Following Step-4 we need to add 1 to the top that is 9 will become 9+1=10

Step-5

As per the final step we need to multiply with 10*9 hence it becomes 90

So 95X95=9025

In my last post I have shown how to multiply with two numbers without using calculator. This is bit advanced post where I will show to make a square a number having five at last without using a calculator.

Say I have to square 15 that is 15X15=225

How to derive this my using simple calculation:

Step-1

Divide the numbers in the below written manner:

Format the number |

Draw a line just after 5

Step-2 Draw a line just after 5 |

Multiply 5*5=25 and write it to the right of the bar

Witting first calculation |

Now add one to the top number here it is 1 so top number becomes 1+1=2

Adding 1 to the top |

Multiply 2*1(that is the left hand side ..this can be done again with multiply two number method)

Hence the result has come to 225.

Now let us try with a big number called 95X95

As per Step-1 and 2 this will look like-

Step-1 |

Step-3

Following step -3 we will get 5*5=25

Step-4

Following Step-4 we need to add 1 to the top that is 9 will become 9+1=10

Step-5

As per the final step we need to multiply with 10*9 hence it becomes 90

So 95X95=9025

How to Square A Number With Last Digit 5?
Reviewed by Animesh Chatterjee
on
July 29, 2011
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