Getting a piano into a truck isn't easy, so we often use a ramp to lower the amount of required force. Three students want to use least effort to put the piano into a truck. They have tried ramps with different length- 3 m, 4 m and 5 m. They have observed that the three of them are needed when the length is 3 m, two of them when the ramp is 4 m and just one when the ramp is 5 m.