What to Memorize in GMAT Quant for the GMAT

we ll here learn how to find sq root of large nos.

first we must know that square of any no. does not end with i.e(last digit of the squared no.) 2,3,7 & 8.


If Last digit of the square (LHS) then last digit of the of sq. root(RHS) or vice versa
1....................................1 or 9
4....................................2 or 8
9....................................3 or 7
6....................................4 or 6
5.................................... 5
0.....................................0

for eg. the sq root of a no. ending in 1 could be 9 or 1. sq.rt of 81 = 9 , and sq. rt of 1 = 1.


nows lets see how to find sq rt of 5184

so in the above example our last digit is 4(LHS) hence the last digit of our ans could be 2 or 8. (RHS).
secondly we know 5184 is between 4900 and 6400. so the sq. rt of both these nos. 70 and 80 respectively. so our ans lies between 70 and 80
that means it could be 72 or 78.
but as we look at our no. 5184 . It is more closer to 4900 than it is to 6400.
therefore our ans has to be 72.