A BOAT IS LYING AT ANCHOR.IT RISES UP EVERY 15SECONDS AS WAVES PASS UNDER IT.IF THE DISTANCE BETWEEN PEAKS IS 3M,HOW LONG AFTER THE FIRST SWELL HAS PASSED UNDER THE BOAT WILL IT PASS UNDER ANOTHER BOAT LYING 150M DIRECTLY AWAY FROM IT
Time = (Distance)/(Wave speed)
Wave speed = (wavelength)/(period)
= 3 m/15s = 0.2 m/s
Take it from there