Question 436902
Let s = the speed of the truck
Then s - 35 = the speed of the train
The time required for the train to travel 90 miles:
t = 90/(s-35)
This is the same time that the truck travels 160 miles:
t = 160/s
Equating the two times gives:
90/(s-35) = 160/s
To make the math simpler, divide both sides by 10:
9/(s-35) = 16/s
Cross-multiply, solve for s:
9s = 16s - 560 -> 7s = 560 -> s = 80
So the speed of the truck is 80 mph (and I think the driver's going to get a speeding ticket!)