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# A driver traveled 1 mile at t ms/ hour. If the speed is

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Senior Manager
Joined: 08 Aug 2005
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A driver traveled 1 mile at t ms/ hour. If the speed is [#permalink]  05 May 2006, 22:13
A driver traveled 1 mile at t ms/ hour. If the speed is t+20ms/hour, it will take 4 minutes less. What Â¡s the value of t?
VP
Joined: 29 Dec 2005
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Re: value of t? [#permalink]  25 May 2006, 18:03
getzgetzu wrote:
A driver traveled 1 mile at t ms/ hour. If the speed is t+20ms/hour, it will take 4 minutes less. What Â¡s the value of t?

good one but little unclear............

t = 10 miles.
VP
Joined: 07 Nov 2005
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Location: India
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Yes got t=10 miles as well.

(1/t)-(1/(t+20))=4/60...

=> t^2+20t-300=0

=> t=10
SVP
Joined: 30 Mar 2006
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T=10

1/t -4/60 = 1/t+20

=> 20/t(t+20) = 1/15
=> t^2 +20t -300 = 0

Solving the equation T= -30 or 10
hence speed is 10
Director
Joined: 10 Oct 2005
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Such problems require you find an equitable equition for time or distance.
In this case it is time which can compared using common variable t.
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