Speed and Distance.

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BTGmoderatorRO: Moderator; Posts: 772; Joined: Wed Aug 30, 2017 6:29 pmFollowed by: 6 members

by BTGmoderatorRO » Sun Jan 07, 2018 7:21 am

If two projectiles are launched at the same moment from 1320 miles apart and travel directly towards each other at 480 miles per hour and 510 miles per hour, respectively, how many minutes will it take for them to meet?

A. 40
B. 44
C. 80
D. 88
E. 90

OA is C

What makes option C correct, I solved and got B.Pls, i need an Expert contribution.

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Source: Beat The GMAT — Problem Solving | Sun Jan 07, 2018 7:21 am

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by [email protected] » Sun Jan 07, 2018 4:55 pm

Hi Roland2rule,

We're told that two projectiles are launched at the same moment from 1320 miles apart and travel directly towards each other at 480 miles per hour and 510 miles per hour, respectively. We're asked for the number of MINUTES it take for them to meet.

This is an example of a 'Combined Rate' question, so you can add the two rates together to determine how much distance each covered IN TOTAL each hour.

Distance = (Total Rate)(Time)
1320 miles = (990 miles/hour)(X HOURS)
1320/990 = X hours
132/99 = X hours
1 33/99 hours = X
1 1/3 hours = X

Since 1/3 of an hour = 20 minutes, the total time for the two projective to meet is 60+20 = 80 total minutes

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8157; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Sun Aug 04, 2019 10:31 am

BTGmoderatorRO wrote:If two projectiles are launched at the same moment from 1320 miles apart and travel directly towards each other at 480 miles per hour and 510 miles per hour, respectively, how many minutes will it take for them to meet?

A. 40
B. 44
C. 80
D. 88
E. 90

OA is C

What makes option C correct, I solved and got B.Pls, i need an Expert contribution.

Since the projectiles are launched simultaneously, we can let t = the travel time for each. We can create the distance equation:

480t + 510t = 1320

990t = 1320

t = 1320/990 = 4/3 hours = 1 1/3 hours = 1 hour 20 minutes = 80 minutes

Answer: C

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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