Let a be the side of the square track.
Perimeter of the square track = 4a
Bajinder runs ten times around the square track and covers 4 km.
i.e., 10 × 4a = 4 km
⇒ 40a = 4 × 1000 m [∵ 1 km = 1000 m]
⇒ a = (4 x 100)/40 m = 100 m
∴ Length of the track = 4a
= 4 × 100 m = 400 m
