Why is this wrong (cal):
A street light is at the top of a 17.0 ft. tall pole. A man 6.2 ft tall walks away from the pole with a speed of 7.0 feet/sec along a straight path. How fast is the tip of his shadow moving when he is 48 feet from the pole?
My sol.:Let x be the distance between the pole and the man.
dx/dt = 7
Let y be the distance between the tip of his shadow and the pole.
We want dy/dt
Using similar triangles,
y/15=x/6.2
6.2y=15x
y=(17/6.2) x
dy/dt = (17/6.2) (7) = 19.19, but this seems to be wrong. Help?

Question

Why is this wrong (cal):
A street light is at the top of a 17.0 ft. tall pole. A man 6.2 ft tall walks away from the pole with a speed of 7.0 feet/sec along a straight path. How fast is the tip of his shadow moving when he is 48 feet from the pole? 
My sol.:Let x be the distance between the pole and the man. 
dx/dt = 7 
Let y be the distance between the tip of his shadow and the pole. 
We want dy/dt 
Using similar triangles, 
y/15=x/6.2 
6.2y=15x 
y=(17/6.2) x 
dy/dt = (17/6.2) (7) = 19.19, but this seems to be wrong. Help?

anonymous · Answer

Those 15s in the beginnings where typos. Regard them as 17.