An elephant weighing 2 tonnes (2 metric tons) and a rabbit weighing 1kg are balanced on a very long, perfectly rigid board.
If the elephant starts walking toward the center at the uniform rate of 1 meter per minute, how many km per hour must the rabbit run in order to maintain the balance?
Remember 1 tonne = 1000 kg
30 km/hr120 km/hr180 km/hr60 km/hr