Find the last digit

rohu27: Legendary Member; Posts: 586; Joined: Tue Jan 19, 2010 4:38 am; Thanked: 31 times; Followed by:5 members; GMAT Score:730

by rohu27 » Wed May 25, 2011 1:38 am

concentrate on only the last digits..

1+4+9+6+5+6+9+4+1+0.... - this cycle repeats for evry 10 numebrs.
1+4+9+6+5+6+9+4+1+0=45*10=450
so last digit is 0
pick A

Have time? https://www.beatthegmat.com/730-q-50-v40 ... 88058.html

Quote

manpsingh87: Master | Next Rank: 500 Posts; Posts: 436; Joined: Tue Feb 08, 2011 3:07 am; Thanked: 72 times; Followed by:6 members

by manpsingh87 » Wed May 25, 2011 1:41 am

vikrantr93 wrote:Find the last digit of the number 1^2 + 2^2 + 3^2 + 4^2 + ... + 99^2

a. 0
b. 1
c. 2
d. 5
e. 3

sum of square of first n natural no. is given as n(n+1)(2n+1)/6;--------1)
here n=99; so submitting n=99 in 1 we have;
99*100*199/6; as the numerator is multiple of 10; therefore its last digit will be 0, hence a

O Excellence... my search for you is on... you can be far.. but not beyond my reach!

Quote

Post new topic Post Reply

• Page 1 of 1

5/5

5 Star (486 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review