Jan lives $x$ floors above the ground floor of a highrise building. It takes her 30 seconds per floor to walk down the

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Vincen: Legendary Member; Posts: 2898; Joined: Thu Sep 07, 2017 2:49 pmFollowed by: 5 members; Thanked: 6 times

by Vincen » Mon May 18, 2020 7:01 am

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Jan lives $x$ floors above the ground floor of a highrise building. It takes her 30 seconds per floor to walk down the steps and 2 seconds per floor to ride the elevator. If it takes Jan the same amount of time to walk down the steps to the ground floor as to wait for the elevator for 7 minutes and ride down, then $x$ equals

A) 4

B) 7

C) 14

D) 15

E) 16

[spoiler]OA=D[/spoiler]

Source: Official Guide

Source: Beat The GMAT — Problem Solving | Mon May 18, 2020 7:01 am

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16206; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

Re: Jan lives $x$ floors above the ground floor of a highrise building. It takes her 30 seconds per floor to walk down

by Brent@GMATPrepNow » Mon May 18, 2020 2:24 pm

Vincen wrote: ↑
Mon May 18, 2020 7:01 am
Jan lives $x$ floors above the ground floor of a highrise building. It takes her 30 seconds per floor to walk down the steps and 2 seconds per floor to ride the elevator. If it takes Jan the same amount of time to walk down the steps to the ground floor as to wait for the elevator for 7 minutes and ride down, then $x$ equals

A) 4

B) 7

C) 14

D) 15

E) 16

[spoiler]OA=D[/spoiler]

Source: Official Guide

Let's first convert 7 minutes to SECONDS in order to have uniform units of measurement.
7 minutes = 420 seconds

Let's start with a word equation
Jan's travel time (in seconds) WALKING down = Jan's travel time (in seconds) via ELEVATOR + 420 seconds

It takes her 30 seconds per floor to walk down the steps and 2 seconds per floor to ride the elevator.
There are x floors
So, WALKING time (in seconds) = 30x
And ELEVATOR time (in seconds) = 2x

Plug values into word equation to get: 30x = 2x + 420
Subtract 2x from both sides to get: 28x = 420
Solve: x = 420/28
= 60/4
= 15

Answer: D

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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Re: Jan lives $x$ floors above the ground floor of a highrise building. It takes her 30 seconds per floor to walk down

by Scott@TargetTestPrep » Sun May 24, 2020 4:54 am

Vincen wrote: ↑
Mon May 18, 2020 7:01 am
Jan lives $x$ floors above the ground floor of a highrise building. It takes her 30 seconds per floor to walk down the steps and 2 seconds per floor to ride the elevator. If it takes Jan the same amount of time to walk down the steps to the ground floor as to wait for the elevator for 7 minutes and ride down, then $x$ equals

A) 4

B) 7

C) 14

D) 15

E) 16

[spoiler]OA=D[/spoiler]

Source: Official Guide

Since 7 minutes = 420 seconds, we can create the equation:

Jan’s time to walk = Jan’s time to ride

30x = 420 + 2x

28x = 420

x = 15

Answer: D

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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