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A conundrum

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A conundrum

by hemant_rajput » Mon Feb 04, 2013 7:45 am
Q18 . A group of 4 person A,B,C and D arrive in a car to a friend's house. The group was forced to park around the corner due to lack of parking space. It was raining heavily and group had only one umbrella. They decide to share it. Two person would go at a time to the friend's house and one of them would come back with umbrella. The process would be repeated unless all four people reach the friends house. If A,B,C and D takes 1,2,5 and 10 min resp. at their fastest speed to go reach the friend's house, what is the minimum time required for all of them to reach the friend's house( A faster person slows down to accompany a slower one)
a. 15
b. 17
c. 22
d. 14

the OA is D but I'm getting B, please help me with this.
I'm no expert, just trying to work on my skills. If I've made any mistakes please bear with me.
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by Jim@StratusPrep » Mon Feb 04, 2013 7:55 am
A and B walk to house - 2 min
A walks back - 1 min
A and C walk to the house - 5 mins
A walks back - 1 min
A and D walk to the house - 10 mins

I get 19, so not sure where the 22 comes from.
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by GMATGuruNY » Mon Feb 04, 2013 8:15 am
hemant_rajput wrote:Q18 . A group of 4 person A,B,C and D arrive in a car to a friend's house. The group was forced to park around the corner due to lack of parking space. It was raining heavily and group had only one umbrella. They decide to share it. Two person would go at a time to the friend's house and one of them would come back with umbrella. The process would be repeated unless all four people reach the friends house. If A,B,C and D takes 1,2,5 and 10 min resp. at their fastest speed to go reach the friend's house, what is the minimum time required for all of them to reach the friend's house( A faster person slows down to accompany a slower one)
a. 15
b. 17
c. 22
d. 14

the OA is D but I'm getting B, please help me with this.
To minimize the total amount of time, each trip back to the car should be taken by the FASTEST person available.

A and B walk to the house = 2 minutes.
A walks back to the car = 1 minute.
C and D walk to the house = 10 minutes.
B walks back to the car = 2 minutes.
A and B walk to the house = 2 minutes.
Total time = 2+1+10+2+2 = 17 minutes.

The correct answer is B.
Last edited by GMATGuruNY on Mon Feb 04, 2013 8:29 am, edited 1 time in total.
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by Jim@StratusPrep » Mon Feb 04, 2013 8:19 am
Looks, spot on.... looks like I needed more thought...
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by hemant_rajput » Mon Feb 04, 2013 8:30 am
hehe...even I used the same approach as GMATguru. Although, my friend corroborate that 14 is the right answer but he was not able to recall the method. So guys if you think 17 is right then I'll just accept it.
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by Jim@StratusPrep » Mon Feb 04, 2013 8:36 am
There is no way to do it in 14, rest in peace.
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by hemant_rajput » Mon Feb 04, 2013 8:42 am
thanks guys for confirming it.
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by Brent@GMATPrepNow » Mon Feb 04, 2013 8:50 am
This question is a rewording of a question I saw several years ago.
The original question involved a flashlight (instead of an umbrella) and the 4 members of U2 (instead of A, B, C and D).

https://www.braingle.com/brainteasers/515/u2.html

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by ceilidh.erickson » Mon Feb 04, 2013 3:58 pm
While Mitch's solution is correct, it's important to note - this is not a question that you're likely to see on the GMAT. The GMAT tends not to ask these mind-teaser type problems, like "you have a fox, a goose, and a bag of flour, and you need to cross a river..." These types of problems do not test any specific mathematical concepts, but instead test sequencing logic. The GMAT does sometimes test logical groupings (OG DS D45, OGQ DS8), but in these cases, they're still testing properties of numbers, and not really the sorting logic itself.

The moral of the story is: don't worry about this type of problem.

(Here's a great cartoon on the subject: https://xkcd.com/1134/ )
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by Tommy Wallach » Tue Feb 05, 2013 12:25 pm
Hey All,

I'd also like to add something, if I could. I notice so many questions on here with bad grammar in them. I'd like everyone reading this to try to turn over this new leaf: If you notice a question with broken grammar, DON'T DO IT! The bad grammar is proof that the person who wrote it doesn't really know the GMAT, and just by reading those questions, you're going to be cementing bad habits of English grammar.

If there weren't enough great material out there, then maybe people would have no choice. But there's plenty! Anything published by any of the major companies, and also stuff on the side (I think GMAT Hacks is pretty great, actually) should be enough for anyone!

-t

P.S. I noticed the bad grammar here when there's no Oxford comma (A, B, C, and D). "Parking space" should be "parking spaces." The next sentence should say "THE group". The next sentence changes to present tense when the previous sentence was past tense. The next sentence says "two person" instead of "two people". And on and on!
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