math
posted by ryan .
a coast guard ship left the port at 30 mph. four hours later a helicopter was dispatched at 90 mph to intercept the ship. how long will it take the helicopter to catch the ship?

Make a chart for the pieces of RT=D that you know.
Rate X Time = Distance
_____________________________________
ship 30 x 30x
chopper 90 x4 90(x4)
You know that at the time the helicopter overtakes the ship that the distances are equal.
30x=90(x4) set distances equal
30x = 90x360 ditribute
60x = 360 subt 90xfrom both sides
x =6 divide by 60
x4 is the helicopter's time so plug in
6 for x
64 = 2
therefore the helicopter will take over
in 2 hours.