From the question it is given that,
Tahir measured the distance around a square field as 200 rods
Length of the rod = 140 cm
So, total distance of square field = 200 × 140
= 28000 cm
Then, length of one side of square field = 28000/4
= 7000 cm
We know that, 1 m = 100 cm
Therefore, side of field = 7000/100
= 70 m