BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

N

Expert replies
by shashank.ism » Mon Feb 08, 2010 7:38 am
If N = 1000^8 - 8, what is the sum of its digits?

a) 200
b) 207
c) 208
d) 209
e) 175
My Websites:
www.mba.webmaggu.com - India's social Network for MBA Aspirants

www.deal.webmaggu.com -India's online discount, coupon, free stuff informer.

www.dictionary.webmaggu.com - A compact free online dictionary with images.

Nothing is Impossible, even Impossible says I'm possible.
Join the discussion
Source: — Problem Solving |

by Brent@GMATPrepNow » Mon Feb 08, 2010 7:47 am
shashank.ism wrote:If N = 1000^8 - 8, what is the sum of its digits?

a) 200
b) 207
c) 208
d) 209
e) 175
1000^8 = (10^3)^8 = 10^24
So, 1000^8 is a number with 1 followed by 24 zeroes.
This means that 1000^8 - 8 is a 24-digit number: 9999999.....9992
This number consists of 23 nines and 1 two.
So, the sum is 23x9 + 2 = 209 (D)
Brent Hanneson - Creator of GMATPrepNow.com
Image
Join the discussion

by ajith » Mon Feb 08, 2010 10:37 am
shashank.ism wrote:If N = 1000^8 - 8, what is the sum of its digits?

a) 200
b) 207
c) 208
d) 209
e) 175
1000^8 = (10^3)^8 = 10^(8*3 ) = 10^24

10^24-8 = 99...(23times)2

Sum of digits= 9*23+2 = 209
Always borrow money from a pessimist, he doesn't expect to be paid back.
Join the discussion