One Saturday morning, Mary cycled from her home in Dublin to Maynooth, and then cycled home along the same route that afternoon. The distance from her home to Maynooth is exactly 10 miles and she cycled at a constant speed of 10 miles per hour in both directions. On Sunday, she decided to make the same cycling trip. However, due to a westerly wind, she cycled at a constant speed of 5 miles per hour when going from Dublin to Maynooth, and at a speed of 15 miles per hour on the return trip from Maynooth to Dublin.
How much longer, in minutes, did the trip take on Sunday?
2007-02-05 08:38:43 · 12 answers · asked by mad dawg 1 in Science & Mathematics ➔ Mathematics
Distance one way = 10
First trip:
T1 = 10/10 + 10/10 = 20/10 = 2 hours
Second trip:
T2 = 10/5 + 10/15 = 40/15 = 2 and 2/3 hours
The trip took 40 minutes, or (60)(2/3) minutes longer on Sunday.
2007-02-05 08:45:59 · answer #1 · answered by MamaMia © 7 · 0⤊ 0⤋
Saturday:
10 Miles * (1 Hour/10 Miles) = 1 Hour from Dublin to Maynooth
10 Miles * (1 Hour/10 Miles) = 1 Hour from Maynooth to Dublin
2 Hours total
Sunday:
10 Miles * (1 Hour/5 Miles) = 2Hour from Dublin to Maynooth
10 Miles * (1 Hour/15 Miles) = 2/3 Hour from Maynooth to Dublin
2 2/3 Hour = 2 Hours and 40 Minutes
So Sunday took 40 minutes longer
2007-02-05 08:42:25 · answer #2 · answered by Mariko 4 · 0⤊ 2⤋
If the route in one direction is 10 miles, and she went 10 mph in both directions on Saturday morning, then her total trip that day was 2 hours (one hour in each direction).
Speed is distance divided by time (s=d/t), so time is distance divided by speed (t=d/s). Mary's total time making the trip on Sunday would have been 10mi/5mph one way and 10mi/15mph the other way. So together it was 10/5 + 10/15 hours, which is 2 + 2/3 hours. So This trip took 2/3 hours longer. 2/3 of 60 minutes is 40 minutes, so that's the answer.
2007-02-05 08:50:46 · answer #3 · answered by Anonymous · 0⤊ 0⤋
The first trip took exactly 2 hours, while the trip on Sunday too 2 and 10/15 hours, so there is an excess of ~0.67 hours, or, if you convert this in minutes, ~40 minutes. Thus, the trip on Sunday is longer by ~40 minutes.
2007-02-05 08:46:40 · answer #4 · answered by Anonymous · 0⤊ 0⤋
40 minutes
2 hours the first day round trip
second day took 2 hours from Dublin and 40 minutes from Maynooth
2007-02-05 08:42:26 · answer #5 · answered by gman1602 3 · 0⤊ 0⤋
Well on Saturday she traveled 20 miles in 2 hours
On Sunday trip there would take 2 hours (5 miles per hour). On the way home it would take her 2/3 of an hour. So it would take her 2/3 of an hour or 40 mins longer.
2007-02-05 08:45:48 · answer #6 · answered by leo 6 · 0⤊ 0⤋
on Sunday she took 2 2/3 hrs so she took 2/3 of an hour extra on Sunday than usual
2007-02-05 08:48:34 · answer #7 · answered by balzan_bernice 1 · 0⤊ 0⤋
1st trip - 20 miles @ 10 mph = 2 hrs
2nd trip:
10 miles @ 5 MPH = 2 hrs
10 miles @ 15MPH = .6667 hrs
.6667 hrs longer on the second trip.
2007-02-05 08:43:20 · answer #8 · answered by mradigan747 2 · 0⤊ 0⤋
Just directly calculate the time taken on each of the four trip legs. (The first two were of course the same.)
2007-02-05 08:49:07 · answer #9 · answered by Curt Monash 7 · 0⤊ 0⤋
45 minutes.
2007-02-05 08:44:32 · answer #10 · answered by jollyrojr 1 · 0⤊ 0⤋