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Re: DS: Prime numbers [#permalink]
11 May 2009, 02:56
if p, s, and t are positive prime numbers, what is the value of p^3s^3t^3? (1) p^3st=728 (2) t=13
(1) 728 = 2*2*2*7*13, so we know p=2, s=7or13, t=13or7. The values for s & t doesn't really matter because we need to find the value of (p*s*t)^3. So, its (2*7*13)^3 Suff (2) nothing about s * t Insuff
So, p^3st=2^3(7)(13) This gives us that p=2, and s=7,t=13 or s=13,t=7. But in either case it doesn't matter, because the order in which we multiply the primes has no effect on the answer. For example, (2)(7)(13) = (2)(13)(7)), yes? So ((2)(7)(13))^3 = ((2)(13)(7))^3 as well.
(2) By itself this is insufficient as it tells us nothing about p or s.
Final Answer, A.
Re: DS: Prime numbers
14 May 2009, 13:11