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A good question on number properties

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A good question on number properties

by dinesh19aug » Fri Aug 13, 2010 4:03 pm
I got this question on knewton test. It is very good question. Here's the question, that I want to share:

3 + 3 + 3 + 2 X 3^2 + 2 X 3^3 + 2 X 3^4 + 2 X 3^5 + 2 X 3^6 + 2 X 3^7 =???

[spoiler]Answer is 3^8

Hint: Find the common terms 3+3+3 can be written as 3^2


Ans: 3^8[/spoiler]
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by selango » Fri Aug 13, 2010 7:35 pm
3 + 3 + 3 + 2 X 3^2 + 2 X 3^3 + 2 X 3^4 + 2 X 3^5 + 2 X 3^6 + 2 X 3^7

3^2+2 X 3^2 + 2 X 3^3 + 2 X 3^4 + 2 X 3^5 + 2 X 3^6 + 2 X 3^7

3^2+3^2(2+6)+3^4(2+6)+3^6(2+6)

3^2+8.3^2+8.3^4+8.3^6

9.3^2+8.3^4(1+9)

3^4+80.3^4

81.3^4=3^4.3^4=3^8
--Anand--
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