Question

a bus travels 36 km in 40 min.if it maintains a uniform speed, how long will it take to cover 216 km ?

Answer 1

36 km  ------>  40 min
216 km ------>  ? min

$\frac{216}{36}*40$ = 240 minutes = 4 hours.

Answer 2

so using unitary method 

36 km is covered in 40 min
so 1 km is covered in 40/36 min
and therefore 
216 km is covered in 40 x 216/36 min = 240 min = 4 hr