TAP 1 TAKES

     
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Tap 1 takes 1.5 hours khổng lồ fill a certain tank with water. Tap 2 fills the same tank with water at a rate X times as fast as tap 1. Tap 1 và tap 2 together take 15 minutes to fill the same tank with water. Find the value of X.A) 1/9B)1/5C) 5D) 9E) 45
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Elite Legendary member Posts: 10392Joined: 23 Jun 2013Location: Palo Alto, CA Thanked: 2867 times Followed by:510 members GMAT Score:800
Hi chaitanya.bhansali,This is an example of a Work Formula question (2 entities sharing a job), which means that we"ll need the Work Formula:Work = (A)(B)/(A+B)We"re given....Tap1 = A = 1.5 hoursTap2 = B = B hours Together = 15 minutesSince the "units" of measure change, I"m going to lớn convert everything into minutes:A = 90 minutesB = B minutesTogether = 15 minutes(90)(B)/(90 + B) = 15Now we do algebra...90B = 1350 + 15B75B = 1350B = 18So B takes 18 minutes to fill the tank on its own. The question asks how much FASTER was B than A?A = 90 minutesB = 18 minutesB does the job in 1 tháng 5 the time, so it"s 5 times faster.Final Answer: CGMAT assassins aren"t born, they"re made,Rich
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GMATGuruNYGMAT Instructor Posts: 15537Joined: 25 May 2010Location: New York, NY Thanked: 13060 times Followed by:1901 members GMAT Score:790
chaitanya.bhansali wrote:Tap 1 takes 1.5 hours khổng lồ fill a certain tank with water. Tap 2 fills the same tank with water at a rate X times as fast as tap 1. Tap 1 và tap 2 together take 15 minutes to lớn fill the same tank with water. Find the value of X.A) 1/9B)1/5C) 5D) 9E) 45
Since Tap 2 fills the tank X times as fast as Tap 1, X = (Tap 2"s rate)/(Tap 1"s rate).The times given are 1.5 hours -- the equivalent of 90 minutes -- và 15 minutes.To make the math easy, let the tank = 90 gallons.Since the 2 taps together take 15 minutes to lớn fill the tank, the combined rate for Tap 1 and Tap 2 = 90/15 = 6 gallons per minute.Since Tap 1 takes 90 minutes to lớn fill the tank, Tap 1"s rate = 90/90 = 1 gallon per minute.Thus:Tap 2"s rate = (combined rate for both taps) - (Tap 1"s rate) = 6-1 = 5 gallons per minute.X = (Tap 2"s rate)/(Tap 1"s rate) = 5/1 = 5.The correct answer is C.
Mitch HuntPrivate Tutor for the GMAT & GREIf you find one of my posts helpful, please take a moment lớn click on the "UPVOTE" icon.Available for tutoring in NYC và long-distance.For more information, please e-mail me at .Student reviews #1Student đánh giá #2Student đánh giá #3


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