How to Find the Square of Number ending with 5?

• 52 = 25

• 152 = 225

• 252 = 625

Now see the similarity. In all these numbers the last two digits are same. That

is 25. The only thing it changes is the first digit.

How to find that?

a) What is 152

?

We know the last two digits of the square will be 25. Now take the first digit of

15; i.e. 1. Multiply 1 with it’s next number. i.e. 2. So 1 x 2 = 2. Answer is 225.

b) What is 252

?

We know the last two digits of the square will be 25. Now take the first digit of

25; i.e. 2. Multiply 2 with it’s next number. i.e. 3. So 2 x 3 = 6. Answer is 625.

c) What is 552

?

(5 x 6) 25 = 3025

d) What is 852

?

(8 x 9) 25 = 7225. Hardly it takes less than 5 seconds. You don’t even need to

write the numbers on the paper.

Try 1052

As usual (10 x 11) 25 = 11025 is the answer. Our usual method will take a

minimum of 30 seconds to do this simple multiplication. Now we can easily

save 25 seconds.

Practice Problems

1. 1152

2. 2055