New to this site ... difficult math problem

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londongq: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Sun Jan 11, 2009 11:01 pm

New to this site ... difficult math problem

by londongq » Sun Jan 11, 2009 11:06 pm

Hello all,

I'm new to this site so hope someone can help me out. I did a quick search and couldn't find a similar questions.

here is the problem; it's been driving me crazy for few days now, i know it looks so simple but i think i'm missing a step.

(1/5) power m * (1/4) power 18 = 1/2(10) power 35

find m?

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Source: Beat The GMAT — Problem Solving | Sun Jan 11, 2009 11:06 pm

londongq: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Sun Jan 11, 2009 11:01 pm

i know it has been mentioned b4 but the answer is not clear

by londongq » Sun Jan 11, 2009 11:35 pm

it becomes 5^-m * 4^-18 = 10^-35/2

why does the right hand side equal 5^-36?

Some please explain this to me?

Appreciate ur help

thanks

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krishdpi: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Fri Oct 03, 2008 12:22 am

by krishdpi » Sun Jan 11, 2009 11:47 pm

Well... A simple way to look at this problem is:

(1/5) ^ m * (1/4) ^ 18 = 1/(2* 10^35)

RH Side: = 1/(2 * 2 ^ 35 * 5 ^ 35)
LF Side : = (1/5 ^ m) * (1/2 ^ 2) ^ 18
= (1/5 ^ m) * (1/2 ^ 36)

So:
1/(5 ^ m) * (1/2 ^ 36) = 1/(2 * 2 ^ 35 * 5 ^ 35)
1/(5 ^ m) = (2 ^ 36) / (2 ^36 * 5 ^ 35)
1/(5 ^ m = 1 / ( 5 ^ 35)
This gives us an answer of m = 35.

Hope this helps.