Searched this forum but could not find this question answered before. Can someone help explain the OA.
A cold water tube can fulfill a pool in C hours; a hot water tube can fulfill it in H hours. C<H. Two tubes together can fulfill the pool in T hours. Which of the following must be true?
I. 0<T<H
II. C<T<H
III. C/2 < T < H/2
OA: I + III
Hot water and Cold Water tubes
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The easier way (IMO) is to plug in numbers. So if C=2 and H=4 (C<H) T will be 4/3 (1/2+1/4=1/T)... Just check with the options and u'll see that I and III are the ones that must be true
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If you want to understand why I and III must be true here (for any numbers), I posted an explanation here:
www.beatthegmat.com/rates-problem-t21746.html
www.beatthegmat.com/rates-problem-t21746.html
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com
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