Area of a square natural lake is 50 sq. kms. A driver wishing to cross the lake diagonally, will have to swim a distance of :

Let the length of the diagonal be x km
Then,
$$\eqalign{ & \Rightarrow \frac{1}{2}{x^2} = 50 \cr & \Rightarrow {x^2} = 100 \cr & \Rightarrow x = 10\,{\text{km}} \cr & \Rightarrow x = \left( {\frac{{10}}{{1.6}}} \right){\text{miles}} \cr & \Rightarrow x = 6.25{\text{ miles}} \cr & \left[ {\because 1{\text{ mile}} = {\text{1.609 km}}} \right] \cr} $$