Problem Solving

1) Which of the following is equal to 955^2

A. 900025

B. 912025

C. 925525

D. 935025

E. 950255

955^2 ==> (1000-45)^2 ==> 1000000 + 45^2 - 90000 ==> 910000 + 45^2. So, the answer should be just above 910000. The only answer closest is B.
Note: We don't need to find the square of 45^2.

Vemuri wrote:955^2 ==> (1000-45)^2 ==> 1000000 + 45^2 - 90000 ==> 910000 + 45^2. So, the answer should be just above 910000. The only answer closest is B.
Note: We don't need to find the square of 45^2.

Nice try Vemuri but risky. Here is a trick for squaring numbers that end in 5.

If 2 digits, such as 15^2 multiply the tenth digit and 1+tenth digit and add 25 to the end.
(1) (2) =2 just add 25 to end 225. If more than 2 digits treat rest of digits as tenth and do the same trick.

So 95 96 and add 25 to end of product. But

95 ( 95+1)

95^2 +95 ( you have another sqare invoing 5 at end)

9 x 10= 90 add 25 to end 9025 +95=9120 don't forget to add the 25 from original problem

912025.

So Never waste time on traditionally muliplying any square that ends in 5

Numbers like 45^2 75^2 85^2 may kill some time on GMAT when solving problems plus a liitle error and you are done.

true.. its vedic mathematics.. quite simple stuff.. thanks for sharing..

https://www.vedicmaths.org/Introduction/ ... #tutorial5

dumb.doofus wrote:true.. its vedic mathematics.. quite simple stuff.. thanks for sharing..

https://www.vedicmaths.org/Introduction/ ... #tutorial5

That is an awesome link! Thanks!

Thanks for the links.