Question

A farmer moves along the boundary of a square field of side 10m in 40sec. What will be the magnitude of displacement of the farmer at the end of 2min 20sec from his intial  position?

Answer 1

in 40 sec he completes 1 round.
in 80 sec he completes 2 round
so in 2min 20sec he will complete 2 1/2 rounds
so his displacement is 20 m

Answer 2

displacement is 3 and 1/2 round 
2 min 20 s - 140 s 
10 m - 40 s
140 s - 3 1/2 rounds