Can you tell me whats 45 x 45 = ?? or 65 x 65 = ?? or 85 x 85 = ??
You can Mentally solve the above problems after learning the trick that I am gonna teach you today.
So here goes the trick
For Example calculating whats 65 x 65 = ???, Step 1 : We'll multiply the two last digits of each number i.e. = 5 x 5 =25 Step 2: Increase 1st digit of any number by 1 & then multiply it with 1 digit of next number, i .e 6 is increased by 1 so it becomes 7 & its product will be 7 x 6 = 42 Step 3: Append those numbers i.e. 42 25 & thats your answer.
Lets take another example to understand is better
For Example calculating whats 95 x 95 = ???, Step 1 : We'll multiply the two last digits of each number i.e. = 5 x 5 =25 Step 2: Increase 1st digit of any number by 1 & then multiply it with 1 digit of next number, i .e 9 is increased by 1 so it becomes 10 & its product will be 10 x 9 = 90 Step 3: Append those numbers i.e. 90 25
Now i am sure you can find square of any number with multiple of 5 mentally just increase the number by 1 & multiply it with next digits 1 st number. Then just at last append 25 to it.
Note: you can only apply this trick to numbers ending with 5 only. |
AuthorA Math Lover!! I have trained students who used to fear from Maths and now are active participant in the Math Contest conducted all around the world Archives
September 2016
Categories |