The area of a square field is 7200 m². How long will a cycle take to cross the field diagonally at a constant rate of 4 km/h?

Correct option is A

Given

area of a square field = 7200 m2

Formula used

Area of square = (side)²

Diagonal of square = √{(side)² + (side)²}

Time = $$\frac{Distance}{speed}$$​​

Solution:

Distance cover = √{7200 + 7200}

=  √14400

=  120 m

Speed of cycle = 4 km/h

​$$= \frac{4 \times 1000}{60}\\\ \\= \frac{400}{6}\\\ \\= \frac{200}{3} \, \text{m/min}$$​​

Time taken by cycle to cover 120 m = 120/(200/3)

​$$= (\frac{120}{1}) × (\frac{3}{200}) \\\ \\= \frac{360}{200} \\\ \\= \frac{9}{5} minutes$$​​