Question

A man walking at the speed of 4 km/hr crosses a square field diagonally in 3 minutes. the area of the field (in m2) is:

Answer 1

Speed = 4 Km/ hr = 4×5/18 m/s = 20/18 m/s
Time = 3 minutes = 180 sec
Distance = Speed × Time
Distance = 20/18 × 180
Distance = 200 m
This distance is equal to diagonal of the square field hence length of diagonal = 200m
Diagonal and two sides of a square forms a right angled triangle with diagonal as it's hypotenuse.
By Pythagoras Theorem
{Side}^2 + {Side}^2 = {Hypotenuse}^2
2 × {Side}^2 = {200m }^2
Transposing 2 to right
{Side}^2 = 40000/2
{Side}^2 = 20000m
Area of square = {Side}^2 = 20000m

Answer 2

Answer is

2000m means

the area of the field is 2000m