1.

1). 3 hours and 30 minutes2). 4 hours3). 4 hours and 15 minutes4). 4 hours and 20 minutes

Answer»

Let the speed of the stream be V km/hr.

Upstream speed = (15 – V) km/hr

Downstream speed = (15 + V) km/hr

6 hours and 30 minutes is 6.5 hours.

To cover 78 upstream, 6.5 hours are required.

We know, Distance = Speed × Time

⇒ 78 = (15 – V) × 6.5

⇒ V = 15 – (78/6.5) = 15 – 12 = 3

⇒ Downstream speed = (15 + V) km/hr = 18 km/hr

∴ Time taken to cover 78 km downstream = 78/18 = 4.333 Time inhours = 4 hours + (1/3) hours = 4 hours and 20 minutes 



Discussion

No Comment Found

Related InterviewSolutions