Venki Ramachandran




How much is 25 x 25 ?

Easy right? You can perhaps do it mentally and come up with the corect answer of 625.


How about 85 x 85 ? Oops. Feel the sudden urge to use a calculator? You don't need to!

The answer is 7225. How about 65 x 65 ? Again, its easy. 4225.


Finding the square of a number ending with "5" (like 25, 75 or 135) is very easy if you know a neat trick.

I am going to explain the trick here. See if you can figure out why it works !

First, notice that when you square a number that ends with 5, the answer always ends in a "25" For example, we saw that 85 squared is 7225 and 65 squared is 4225. So any number that ends with a "5", when squared, will result in a number whose last two digits are "25"

Now coming to the the remaining digit. In 25 x 25, the first digit is "2". In 65 x 65, the first digit is 6. To find the square, we MULTIPLY the first digit by the number that NORMALLY FOLLOWS it in the number line. For example, look at 25. The first digit is 2 and the number that normally follows it in the number line is 3. So 25x 25 = 2x3 = 6, followed by a 25 = 625.

Likewise, 65 x 65. 6 is followed by 7 in the number line. 6 x 7 = 42. So the answer we are looking for is 4225 !

Just try out 55 squared or 115 squared ! Easy eh!

Here's my question for you. WHY DOES IT WORK. Click HERE to see why it works. Would this work for the squares of other numbers?


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