
2x2 System word problem?
An underwater(but near the surface) explosion is detected by sonar on a ship 30s before it is heard on deck. If sound travels at 5,000 ft/s in water and 1,000 ft/s in air, how far is the ship from the explosion?
All I need is the equations and I'll be aright to go from their.

Let $\displaystyle t$ be equal to the time it takes to be heard by the sonar.
We then have that the time for it to be heard on deck is $\displaystyle t + 30$.
$\displaystyle v = \frac {d}{t}$
Therefore:
$\displaystyle d = vt$
And since the distances are equal:
$\displaystyle 1000(t + 30) = 5000t$
Now solve for $\displaystyle t$ to get:
$\displaystyle 4000t = 30000$
$\displaystyle t = 7.5$
Now just plug that into the equation $\displaystyle d = vt$ to get:
$\displaystyle d = 5000(7.5)$
$\displaystyle d = 37,500$ feet