Find the length of a rope by which a cow must be tethered in order that it may be able to graze an area of 9856 sq meters.

• A. 14m
• B. 16m
• C. 76m
• D. 56m

Answer: (D)

clearly the cow will graze a circular field of area 9856 sq m and radius equal to the length of the rope.
Let the length of the rope be r mts  then,
$r^2$ = 9856
$r^2$ = (9856 × 7) / 22 = 3136
r = 56 m