Bunuel
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If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]24 Oct 2019, 02:14
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If \(\frac{8^r}{4^s}=2^t\), then what is r in terms of s and t ?
A. \(s + t + 1\)
B. \(s + t + 5\)
C. \(\frac{2s+t}{3}\)
D. \(\frac{2st}{3}\)
E. \(\frac{s}{2}+\frac{t}{4}\)
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lacktutor
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Joined: 25 Jul 2018
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If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]24 Oct 2019, 02:45
Mohammadmo wrote:
2^3r /2^2s=2^t
3r/2s=t
r=2st/3
Option D
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\(\frac{2^{3r}}{2^{2s}}= 2^{t}\)
—>\(2^{3r—2s}= 2^{t}\)
3r—2s= t
r=\(\frac{( 2s+ t )}{3}\)
The answer is C.
Mohammadmo
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Re: If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]24 Oct 2019, 02:29
2^3r /2^2s=2^t
3r/2s=t
r=2st/3
Option D
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fauji
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Re: If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]24 Oct 2019, 03:41
Approach:
Simplify the given equation:
\(\frac{8^r}{4^s} =2^t --> 2^3 ^r=2^t*2^2 ^s\)
\(3r = t + 2s\)
\(r = \frac{2s+t}{3}\)
IMO Option C it is!
lorenz955
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Joined: 07 Jan 2019
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Re: If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]24 Oct 2019, 09:04
Q: 8^r/4^s=2^t
8^r=2^3r and 4^s=2^2s
so we have: 2^3r/2^2s=2^t
for the rules of the exponents--->x^y/x^z=x^(y-z) this means 2^3r/2^2s=2^(3r-2s)
2^(3r-2s)=2^t---->3r-2s=t---->r=(t+2s)/3
hope this helps.
ScottTargetTestPrep
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Re: If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]29 Oct 2019, 07:24
Expert Reply
Bunuel wrote:
If \(\frac{8^r}{4^s}=2^t\), then what is r in terms of s and t ?
A. \(s + t + 1\)
B. \(s + t + 5\)
C. \(\frac{2s+t}{3}\)
D. \(\frac{2st}{3}\)
E. \(\frac{s}{2}+\frac{t}{4}\)
Simplifying the equation, we have:
2^(3r)/2^(2s) = 2^t
2^(3r-2s) = 2^t
3r - 2s = t
3r = 2s + t
r = (2s + t)/3
Answer: C
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Kinshook
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Re: If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]29 Oct 2019, 07:50
Bunuel wrote:
If \(\frac{8^r}{4^s}=2^t\), then what is r in terms of s and t ?
A. \(s + t + 1\)
B. \(s + t + 5\)
C. \(\frac{2s+t}{3}\)
D. \(\frac{2st}{3}\)
E. \(\frac{s}{2}+\frac{t}{4}\)
If \(\frac{8^r}{4^s}=2^t\), then what is r in terms of s and t ?
\(2^{3r-2s} = 2^t\)
3r -2s = t
\(r = \frac{2s + t}{3}\)
IMO C
TheNightKing
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Re: If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]14 Nov 2019, 19:00
Bunuel wrote:
If \(\frac{8^r}{4^s}=2^t\), then what is r in terms of s and t ?
A. \(s + t + 1\)
B. \(s + t + 5\)
C. \(\frac{2s+t}{3}\)
D. \(\frac{2st}{3}\)
E. \(\frac{s}{2}+\frac{t}{4}\)
Just take 8/4=2 which makes r=s=t=1
Only Option C works.
gmatclubot
Re: If 8^r/4^s =2^t, then what is r in terms of s and t ?[#permalink]
14 Nov 2019, 19:00