A deer is standing 70 meters in from the west end of a tunnel. The deer sees a train approaching from the west at a constant speed ten times the speed the deer can run. The deer reacts by running toward the train and clears the exit when the train is 40 meters from the tunnel. If the deer ran in the opposite direction it would barely escape out the eastern entrance just as the train came out of the eastern entrance. How long is the tunnel in meters?
Pick one.
A) 160
B) 240
C) 520
D) 190
E) 720
Let x be the length of the tunnel.   When the deer runs 70 meters west, the train goes 700 meters to a point 40 meters from the west entrance of the tunnel.   When the deer runs east, the deer runs x-70 meters while the train goes x + 700 + 40 meters.   x + 700 + 40 = 10(x-70)   9x = 1440   x = 160 meters   The answer is 160.
<result>A</result>
A deer is standing 70 meters in from the west end of a tunnel. The deer sees a train approaching from the west at a constant speed ten times the speed the deer can run. The deer reacts by running toward the train and clears the exit when the train is 40 meters from the tunnel. If the deer ran in the opposite direction it would barely escape out the eastern entrance just as the train came out of the eastern entrance. How long is the tunnel in meters?