Speed and Distance.

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

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