Exponents

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kaf: Senior | Next Rank: 100 Posts; Posts: 53; Joined: Mon Feb 09, 2009 12:18 am; Thanked: 1 times

by kaf » Wed Mar 11, 2009 4:36 am

Can someone please explain this for me

5^21 * 2^22 = 2 * (5^21 * 2^21)

and if you can kindly point me to a good tutorial for exponents

thanks

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Source: Beat The GMAT — Problem Solving | Wed Mar 11, 2009 4:36 am

zephir21: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Tue Mar 10, 2009 2:24 am; Thanked: 2 times

by zephir21 » Wed Mar 11, 2009 5:01 am

Do this way to understand :

x^n = x*x*x*x.....*x n times

so 5^21 * 2^22 = 5^21 * ( 2 * 2^21)
As multiplication is associative, you can take the 2 out...

So 5^21 * 2^22 = 2 * (5^21 * 2^21)

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marcusking: Master | Next Rank: 500 Posts; Posts: 106; Joined: Wed Feb 04, 2009 6:09 am; Location: Louisville, KY; Thanked: 8 times

Re: Exponents

by marcusking » Wed Mar 11, 2009 8:31 am

kaf wrote:Can someone please explain this for me

5^21 * 2^22 = 2 * (5^21 * 2^21)

and if you can kindly point me to a good tutorial for exponents

thanks

remember raising a number to a power is just a multiplication. Multiplication operations can be ordered any way and still achieve the same result.

2*3*5 = 3*5*2

In this case we are removing one of the *2 operations in the term 2^22 and simply moving out by itself

think about it like this 2^3 = 2*(2^2)
thus 2^22 is the same as 2*(2^21)

the equation could be written as 5^21 * 2^22 = 5^21 (2 * 2^21) or
5^21 * 2^22 = 2^21 (2 * 5^21) all are saying the same thing just different ways.

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