Mr. Wayne bungee jumps from the top of a building straight

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BTGmoderatorLU: Moderator; Posts: 2505; Joined: Sun Oct 15, 2017 1:50 pm; Followed by:6 members

Mr. Wayne bungee jumps from the top of a building straight

by BTGmoderatorLU » Sat May 04, 2019 6:58 pm

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Source: Economist GMAT

Mr. Wayne bungee jumps from the top of a building straight to the ground at a constant speed. 3 seconds after he starts plummeting he passes the 20th floor. 15 seconds after he starts plummeting he passes the 5th floor. Each floor is 3 meters high. What is Mr. Wayne's speed in meters per second?

A. 3
B. 3.75
C. 4
D. 4.25
E. 5

The OA is B

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Source: Beat The GMAT — Problem Solving | Sat May 04, 2019 6:58 pm

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Ian Stewart: GMAT Instructor; Posts: 2623; Joined: Mon Jun 02, 2008 3:17 am; Location: Montreal; Thanked: 1090 times; Followed by:355 members; GMAT Score:780

by Ian Stewart » Sun May 05, 2019 5:39 am

In 15-3 = 12 seconds, he passes 20 - 5 = 15 floors. If each floor is 3 meters, he covers a distance of 45 meters. So his speed is 45/12 = 15/4 = 3.75 m/s.

Of course if each floor is 3 meters high, it's not clear what it means to 'pass a floor' (when during the 3 meters do we consider the floor to have been 'passed'?), but I imagine the interpretation above is what is intended.

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Sun May 12, 2019 6:13 pm

BTGmoderatorLU wrote:Source: Economist GMAT

Mr. Wayne bungee jumps from the top of a building straight to the ground at a constant speed. 3 seconds after he starts plummeting he passes the 20th floor. 15 seconds after he starts plummeting he passes the 5th floor. Each floor is 3 meters high. What is Mr. Wayne's speed in meters per second?

A. 3
B. 3.75
C. 4
D. 4.25
E. 5

The OA is B

We can see that Mr. Wayne is descending |5 - 20|/|15 - 3| = 15/12 = 5/4 floors per second. Since each floor is 3 meters, he's descending 3 x 5/4 = 15/4 = 3.75 meters per second.

Answer: B

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