two trains leave the same station at 12 PM going in opposite directions. one travels at 45 mph and the other at 60 mph. at what time would they be 2100 miles apart..i dont understand it.
2007-04-26 19:50:42 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
let both the trains travel for x hours to be 2100 m apart , therefore
distance by first train= 45x
distance by second train=60x
total distance between two after x hours = 2100 m
therefore 2100=45x+60x
and therefore x= 2100/105=20
therefor the trains travel 20 hours and the time would be 8 AM
2007-04-26 19:56:27 · answer #1 · answered by Anonymous · 0⤊ 0⤋
first add 45 mph and 60 mph, which would be equal to 105 mph. Then divide 2100 miles by 105 miles per hour to determine the no. of hours to add to 12 PM, which is equal to 20. add 20 hours to 12 PM then you will get 8 AM! it's that simple! hope it helps you!
2007-04-27 04:03:20 · answer #2 · answered by prophessor 3 · 0⤊ 0⤋
since they are going in opposite directions on the same track, you cna add their velocities to get the rate at which they are moving away from each other. To see this, think about one hour from now. Train N has gone 60 miles north, and train S has gone 45 miles south, so they are 105 miles apart. t = D/r = 2100/105 = 20 hours.
2007-04-27 02:58:38 · answer #3 · answered by holdm 7 · 0⤊ 0⤋
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45x m/h + 60x m/h = 2100 m
105x m/h = 2100 m
x=20 h
Add 20 hours to 12 PM and get 8 AM the next day.
2007-04-27 03:04:01 · answer #4 · answered by druid 7 · 0⤊ 0⤋
distance=velocity*time
45t+60t=2100
105t=2100
t=2100/105
=20 hours
if 12pm is midnight then 20:00 pm.
if 12pm is noon, then 8:00 am.
2007-04-27 02:59:20 · answer #5 · answered by iyiogrenci 6 · 0⤊ 0⤋