A spectator watches a rowing race from the edge of a river bank, standing beside the finish line marker. The lead boat is moving in a straight line that is 36 m from the river bank. Give an expression for d, the distance of the boat from the spectator, in terms of r , the distance remaining in the race.
Andrew started walking east at 3 km/h. 2 hours later Brian left the same place, but walked north at 5 km/h. Give an expression for d , the distance between Andrew and Brian, in terms of t , the time since Brian started walking.