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• ### $450 Tuition Credit & Official CAT Packs FREE December 15, 2018 December 15, 2018 10:00 PM PST 11:00 PM PST Get the complete Official GMAT Exam Pack collection worth$100 with the 3 Month Pack ($299) • ### FREE Quant Workshop by e-GMAT! December 16, 2018 December 16, 2018 07:00 AM PST 09:00 AM PST Get personalized insights on how to achieve your Target Quant Score. # What is the sum of digits of number 10^28 – 28?  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics Author Message TAGS: ### Hide Tags Current Student Joined: 11 May 2008 Posts: 545 What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 22 Jul 2008, 18:09 6 00:00 Difficulty: 15% (low) Question Stats: 79% (01:10) correct 21% (01:28) wrong based on 156 sessions ### HideShow timer Statistics What is the sum of digits of number 10^28 - 28? (A) 227 (B) 228 (C) 236 (D) 237 (E) 243 ##### Most Helpful Community Reply Current Student Joined: 11 May 2008 Posts: 545 Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 23 Jul 2008, 04:08 2 4 100=10^2 1000=10^3. so 100-28=72 . so sum= 9 1000-28=972. sum= 9+9 so 10^28= 9+9+9......27times( i.e 28 -1 times)= 27*9=243 ##### General Discussion Director Joined: 12 Jul 2008 Posts: 505 Schools: Wharton Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 22 Jul 2008, 19:30 arjtryarjtry wrote: What is the sum of digits of number 10^28-28? (A) 227 (B) 228 (C) 236 (D) 237 (E) 243 It will be 9*26+7+2 = 243 E VP Joined: 28 Dec 2005 Posts: 1448 Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 23 Jul 2008, 04:03 i dont quite follow ... isnt 10^28 just 1 followed by 28 zeroes ... i.e. the sum of the digits of that number would be just 1, no ? Senior Manager Joined: 06 Apr 2008 Posts: 382 Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 23 Jul 2008, 04:04 pmenon wrote: i dont quite follow ... isnt 10^28 just 1 followed by 28 zeroes ... i.e. the sum of the digits of that number would be just 1, no ? Its 10^28 - 28 So number will be 26 9s followed by 72 whose sum is 243 Intern Joined: 09 Feb 2011 Posts: 15 Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 09 Feb 2011, 12:09 1 What is the sum of digits of number 10^28 – 28? (A) 227 (B) 228 (C) 236 (D) 237 (E) 243 Manager Joined: 27 Oct 2010 Posts: 118 Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 09 Feb 2011, 13:13 1 1000-28=972 for 3 zeroes = 9+7+2 for 28 zeroes = 26*9+7+2=27*9=..3 E SVP Status: The Best Or Nothing Joined: 27 Dec 2012 Posts: 1825 Location: India Concentration: General Management, Technology WE: Information Technology (Computer Software) Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 20 Apr 2014, 20:29 $$10^{28}-28$$ This expression will give all 9's with 72 at the end 99999999......72 Addition of all 9's with 72 will always give a number which is divisible by 9 Only option E = 243 stands out Answer = E _________________ Kindly press "+1 Kudos" to appreciate Math Expert Joined: 02 Sep 2009 Posts: 51218 Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 20 Apr 2014, 22:57 EMPOWERgmat Instructor Status: GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Joined: 19 Dec 2014 Posts: 13095 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: What is the sum of digits of number 10^28 – 28? [#permalink] ### Show Tags 23 Feb 2015, 22:08 1 Dear Moderators, I agree with the correct answer that is given in the thread, but could one of you place it in the original post - I'm sure that other users would like to have it there. GMAT assassins aren't born, they're made, Rich _________________ 760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com # Rich Cohen Co-Founder & GMAT Assassin Special Offer: Save$75 + GMAT Club Tests Free
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Re: What is the sum of digits of number 10^28 – 28?  [#permalink]

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24 Feb 2015, 03:41
EMPOWERgmatRichC wrote:
Dear Moderators,

I agree with the correct answer that is given in the thread, but could one of you place it in the original post - I'm sure that other users would like to have it there.

GMAT assassins aren't born, they're made,
Rich

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Done. Thank you.
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What is the sum of digits of number 10^28 – 28?  [#permalink]

### Show Tags

03 Oct 2018, 01:26
arjtryarjtry wrote:
What is the sum of digits of number 10^28 - 28?

(A) 227
(B) 228
(C) 236
(D) 237
(E) 243

Such question may very well be dealth with Induction method

$$10^2-28 = 100-28 = 72$$ i.e. no digit as 9 and last two digits are 7 and 2

$$10^3-28 = 1000-28 = 972$$ i.e. One digit as 9 and last two digits are 7 and 2

$$10^4-28 = 10000-28 = 9972$$ i.e. Two digits as 9 and last two digits are 7 and 2

---
---

$$10^{28}-28 =$$ Twenty six digits as 9 and last two digits are 7 and 2

i.e.e Sum of digits $$= 26*9 +7+2 = 243$$

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What is the sum of digits of number 10^28 – 28? &nbs [#permalink] 03 Oct 2018, 01:26
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