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# A company’s four cars running 10 hrs a day consume 1200 lts of fuel in

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Intern
Joined: 04 Oct 2017
Posts: 49
Re: A company’s four cars running 10 hrs a day consume 1200 lts of fuel in  [#permalink]

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28 Aug 2018, 08:23
sushforgmat wrote:
Bunuel wrote:
Bunuel wrote:
A company’s four cars running 10 hrs a day consume 1200 lts of fuel in 10 days. In the next 6 days, the company will need to run 9 cars for 12 hrs each so it rents 5 more cars which consume 20% less fuel than the company’s four cars. How many lts of fuel will be consumed in the next 6 days?

(A) 1200 lt
(B) 1555 lt
(C) 1664 lt
(D) 1728 lt
(E) 4800 lt

Kudos for a correct solution.

VERITAS PREP OFFICIAL SOLUTION:

First let’s try to figure out what is meant by ‘consume 20% less fuel than the company’s cars’. It means that if company’s each car consumes 1 lt per hour, the hired cars consume only 4/5 lt per hour. So renting 5 more cars is equivalent to renting 4 cars which are same as the company’s cars. Hence, the total number of cars that will be run for the next 6 days is 8 company-equivalent cars.

4 cars running 10 hrs for 10 days consume 1200 lt of fuel

8 cars running 12 hrs for 6 days consume x lt of fuel

$$x = 1200*(\frac{8}{4)}*(\frac{12}{10})*(\frac{6}{10}) = 1728$$ lt

We multiply by 8/4 because more cars implies more fuel so we multiply by a number greater than 1.

We multiply by 12/10 because more hours implies more fuel so we multiply by a number greater than 1.

We multiply by 6/10 because fewer days implies less fuel so we multiply by a number smaller than 1.

Why can't we interpret the question as below:
The question says "5 more cars which consume 20% less fuel than the company’s four cars" but it doesn't say "5 more cars EACH OF WHICH consumes 20% less fuel than EACH OF the company's four cars".

What I mean to say is it could be interpreted as "all the 5 new cars consume 80% of what all the four cars consume"

If we interpret it that way then it should be "1.8*fuel consumed by 4 cars = 864*1.8 = 1555.2 lt"

Any thoughts?

I interpreted this as above and opted for option B.
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Joined: 11 Aug 2018
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Location: India
Schools: HBS, Stanford
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Re: A company’s four cars running 10 hrs a day consume 1200 lts of fuel in  [#permalink]

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09 Sep 2018, 03:13
can someone explain where I am wrong
let's say if 4 cars consume 100 lt then 5 cars will consume 80lt as 20% less of 100 is 80lt. now if I want to convert efficiency into cars as official explanation has done I need to say 100 liters is consumed by 4 cars so if fuel gets dropped to 80 then cars would be 3.2 ie 100/4=80/x or x= 80/100*4= 3.2 please explain what I am missing
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Re: A company’s four cars running 10 hrs a day consume 1200 lts of fuel in &nbs [#permalink] 09 Sep 2018, 03:13

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