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Carlos runs a lap around the track in x seconds. His second

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GMAT Club Legend
GMAT Club Legend
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Joined: 07 Jun 2014
Posts: 4750
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
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Carlos runs a lap around the track in x seconds. His second [#permalink] New post 19 Aug 2018, 03:49
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Question Stats:

20% (00:50) correct 80% (01:29) wrong based on 10 sessions
Carlos runs a lap around the track in x seconds. His second lap is five seconds slower than the first lap, but the third lap is two seconds faster than the first lap. What is Carlos’s average (arithmetic mean) number of minutes per lap, in terms of x?

(A) \(x - 1\)
(B) \(x + 1\)
(C) \(\frac{x-1}{60}\)
(D) \(\frac{x+1}{60}\)
(E) \(\frac{x+3}{60}\)
[Reveal] Spoiler: OA

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Intern
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Joined: 07 Sep 2018
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Kudos [?]: 1 [0], given: 5

Re: Carlos runs a lap around the track in x seconds. His second [#permalink] New post 16 Sep 2018, 00:05
answer must be c , if not pls. explain??
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 07 Jun 2014
Posts: 4750
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 93

Kudos [?]: 1659 [0], given: 396

CAT Tests
Re: Carlos runs a lap around the track in x seconds. His second [#permalink] New post 16 Sep 2018, 14:06
Expert's post
Explanation

Carlos’s lap times can be expressed as x, x + 5, and x – 2. (Remember, slower race times are greater numbers, so “five seconds slower” means plus 5, not minus 5!) Average the lap times:

\(\frac{x+(x+5)+(x-2)}{3}=\frac{3x+3}{3}=x+1\)

His average time is x + 1 seconds. But the question requires minutes. Since there are 60 seconds in a minute, divide by 60 to get \(\frac{x+1}{60}\), or choice (D).
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Sandy
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Re: Carlos runs a lap around the track in x seconds. His second   [#permalink] 16 Sep 2018, 14:06
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Carlos runs a lap around the track in x seconds. His second

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