submarine A starts at (1000x,0y,0z) goes towards (0x,100y,1000z). It travels 72km/hour = 20m/sec. If submarine B travels at the exact same speed, what should its starting point be to reach (0x,0y,1000z) at the exact same time submarine A reaches (0x,0y,1000z)?

Answer 1

If A is going from (1000,0,0) to (0,100,1000) it will never reach (0,0,1000).
Anyway, when you decide how far A has to go, divide that distance by 72 to get the time needed.

Since you don't say how far B has to travel, it's tough to say how fast it needs to go ...

Answer 2

Steve,

You are right that A will never reach (0,0,1000). It was a typo, I meant to say (0,100,1000). But the question is not to find out how fast B needs to go. Ive already said its going the exact same speed as A. 20m/sec. Im trying to find out what should the starting point for B be such that if A and B are travelling 20m/sec, B will reach (0,0,1000) when A reaches (0,100,1000).

Answer 3

Oh, yeah. But the starting point can be anywhere on a sphere centered at B's destination.