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SAT prep question on equations

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mingshum
Senior Member

USA
29 Posts

Posted - 01/10/2009 : 17:44:09

If 18

18 = r

t where r and t are positive integers and r > t, which of the following could be the value of rt?

A)18
B)36
C)108
D)162
E)324

I squared both sides of the equation and came up with 3 to the sixth power times 2

= r

t

So I concluded that r = 3

and t = 2

thus rt = 216 which is not a choice! The answer is 108. Where did my reasoning go wrong??

Mrspi
Advanced Member

USA
998 Posts

Posted - 01/10/2009 : 18:19:08

quote:
Originally posted by mingshum

If 1818 = rt where r and t are positive integers and r > t, which of the following could be the value of rt?

A)18
B)36
C)108
D)162
E)324

I squared both sides of the equation and came up with 3 to the sixth power times 2= rt

So I concluded that r = 3and t = 2 thus rt = 216 which is not a choice! The answer is 108. Where did my reasoning go wrong??