From the figure, it can be observed that the horse can graze a sector of 90° in a circle of 5 m radius.

Area that can be grazed by horse

= Area of sector OACB

Area that can be grazed by the horse when length of rope is 10 m long

Increase in grazing area = (78.5 − 19.625) m^{2} = 58.875 m^{2}