The rate tells us that, in every 1 hour, 40km. But she travels for 3 hours, and in each of those three hours she goes 40km. 40km for the first hour, 40km for the second, 40km for the third ... 3 * 40km = 120km.
D=RT
D=(40 km/hr.) (3hrs)
=[40(3)] multiply = d=120 km is the distance she traveled on her bike.
