Exponents....almost got it! NEED HELP

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relaxin99: Senior | Next Rank: 100 Posts; Posts: 73; Joined: Tue Sep 16, 2008 4:33 pm; Thanked: 2 times

by relaxin99 » Wed Sep 24, 2008 11:43 pm

5^21 * 4^11 = 2 * 10^n

I work it out but i always get caught at the end and stuck...thanks guys

Source: Beat The GMAT — Problem Solving | Wed Sep 24, 2008 11:43 pm

relaxin99: Senior | Next Rank: 100 Posts; Posts: 73; Joined: Tue Sep 16, 2008 4:33 pm; Thanked: 2 times

by relaxin99 » Wed Sep 24, 2008 11:44 pm

the question asks what is n, sorry....so solve for n

Morgoth: Master | Next Rank: 500 Posts; Posts: 316; Joined: Mon Sep 22, 2008 12:04 am; Thanked: 36 times; Followed by:1 members

by Morgoth » Thu Sep 25, 2008 12:50 am

relaxin99 wrote:5^21 * 4^11 = 2 * 10^n

I work it out but i always get caught at the end and stuck...thanks guys

5^21 * 4^11 = 2 * 10^n

5^21 * 2^22 = 2* 10^n

5^21 * 2^21 * 2 = 2 * 10^n

10^21 * 2 = 2* 10^n

compare the two sides

n = 21

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