Number Systems

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Number Systems

by sukhman » Sat Oct 12, 2013 5:15 am
Find the maximum value of n such 157!is perfectly divisible

1. by 12^n Answer A 77 B 76 C 75 D 78

2. 18^n Answer A37 B 38 C 39 D 40
Source: — Problem Solving |

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by sukhman » Mon Oct 14, 2013 12:15 pm
anybody please reply

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by sanjoy18 » Mon Oct 14, 2013 12:22 pm
1 C
2 A

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by sukhman » Tue Oct 15, 2013 5:08 am
could you explain in detail please

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by theCodeToGMAT » Tue Oct 15, 2013 5:46 am
Sukhman, as advised by Experts, please post ONLY ONE question per thread; this is required to avoid any confusion that may creep in while discussing multiple questions in a same thread.


Q1:

12 = 2 x 2 x 3

Lets find out the power of "3" in 157!
157/3 = 52
52/3 = 17
17/3 = 5
5/3 = 1
So,52+17+5+1 = 75

We know that using the same method if we calculate the value for power of "2" then it would be much greater than 75.

So, we can conclude that we need n = 75 to have prefect divisible
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by theCodeToGMAT » Tue Oct 15, 2013 5:50 am
Q2:

18 = 3 x 3 x 2

Lets find out the power of "3" in 157!
157/3 = 52
52/3 = 17
17/3 = 5
5/3 = 1
So,52+17+5+1 = 75

We know that using the same method if we calculate the value for power of "2" then it would be much greater than 75.

Now, we know that 3^75 would be in numerator. So, we would need n=37

If we take n=38 then the situation will become 3^75/3^76

So, 37
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by sukhman » Tue Oct 15, 2013 7:26 am
point noted , but this was actually posted before , many thanks .....