Truck Problem

[Dee-M-See]

At noon an unloaded truck leaves Depot A for for Depot B
345 Miles away at a speed of 70mph
60 mins later a loaded truck leaves Depot B for Depot A at 55mph
Both trucks maintain a constant speed using the same road
At what time will the trucks pass each other

[Aperio]

Time t is when B leaves.

At time t: A has travelled (70+70t) miles and B has travelled 55t miles. This must be equal to distance between A and B.

70 + 70t +55t=345; t=(345 -70)/12 hrs

[Tenter]

3.12

[pquinlan]

Thye pass at 3:12 pm.

Distance = speed x time (miles = mph x hrs)

After 1 hour, the unloaded truck has travelled 70 miles so there are 345-70 = 275 miles between them when the loaded truck leaves depot B at 1 pm. They pass when their added distance = 275, i.e.

70t+55t = 275 (t is time after 1 pm)
t = 275/125 = 2.2 hours

So they pass 2.2 hrs after 1 pm which is 3:12 pm.

[Dustybun]

what's the relevance of one truck being loaded and the other unloaded? or is this a red herring?
Confused of Croydon!! :o)

[Dee-M-See]

Thank you for your answers
I think the difference between loaded and unloaded, is that the loaded truck would presumably travel slower

[sddsddean]

The second truck will pass the first at the first VOSA weighbridge and laugh at the driver of the first truck being done for no speed limiter and driving over 56mph!!!

[Dustybun]

I'm so glad I arxed!! lol :o)