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What is the sum of digits of number 10^28 – 28?

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arjtryarjtry
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What is the sum of digits of number 10^28 – 28? [#permalink] New post   22 Jul 2008, 19:09
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What is the sum of digits of number 10^28 - 28?

(A) 227
(B) 228
(C) 236
(D) 237
(E) 243
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E
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arjtryarjtry
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Re: What is the sum of digits of number 10^28 – 28? [#permalink] New post   23 Jul 2008, 05:08
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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
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Re: What is the sum of digits of number 10^28 – 28? [#permalink] New post   09 Feb 2011, 14:13
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1000-28=972
for 3 zeroes = 9+7+2
for 28 zeroes = 26*9+7+2=27*9=..3
E
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Re: What is the sum of digits of number 10^28 – 28? [#permalink] New post   20 Apr 2014, 21:29
\(10^{28}-28\)

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
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Re: What is the sum of digits of number 10^28 – 28? [#permalink] New post   20 Apr 2014, 23:57
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loveparis wrote:
What is the sum of digits of number 10^28 – 28?

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


Similar questions to practice:
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the-sum-of-the-digits-of-64-279-what-is-the-141460.html
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10-25-560-is-divisible-by-all-of-the-following-except-126300.html
if-x-is-a-positive-integer-and-10-x-74-in-decimal-notation-61013.html

Hope it helps.
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What is the sum of digits of number 10^28 – 28? [#permalink] New post   03 Oct 2018, 02:26
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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 \(= 26*9 +7+2 = 243\)

Answer: Option E
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Re: What is the sum of digits of number 10^28 28? [#permalink] New post   01 Aug 2022, 02:31
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