jsphcal wrote:
Two dune buggies start out accross the desert at the same time. They drive in a straight line at 25 miles per hour for two hours. Dune buggy A then stops for an hour while dune buggie B continues on at the same steady rate. After and hour, buggy A begins to moving again in the same straight line as B, but this time at a constant speed of 30 miles per hour. If both Dune buggies hold their rates and drive in the same line, how long, in hours, will it take for A to catch up to B?
A. 1
B. 2
C. 2.5
D. 4
E. 5
i calculated how far both buggies drove for the first two hours:
D=Rate x Time
25 miles/hr x 2hrs = 50 miles
then while Buggy A stopped for 1 hour, buggy B drove another 25 miles
so Buggy A is behind by 25 miles when it started and since buggy A is now at 30 miles per hour,
30MPH-25MPH = 5 miles per hour more that buggy A will be gaining on buggy B with each hour.
so it will take Buggy A 5hrs to catch up or make up 25 miles lost or 5 x 5, but the correct answer is
C)2.5
how come?
if there is a better approach to solving this problem, please advise.
thank you for your help.
Both A & B have travelled at same rate 25mph for 2hrs...so they have covered 50miles equally...thats not the question right now
A takes rest for 1 hr and by then since B is still travelling, B has covered 75miles...
After 2 hrs, if we consider both A & B ( with A travelling at 30mph and an hour late, B travelling at 25mph + 1 more hr than A) we need to find out when they will meet
"If both Dune buggies hold their rates and drive in the same line, how long, in hours, will it take for A to catch up to B?"so
Hours 1 2 3 4 5 6
A 25 50 B 80 120 150
B 25 50 75 100 125 150
so somewhere between 4th and 5th hr from starting they meet
and after first 2 hrs, means 2.5(approx) from 2nd hr...