Question : Find the time taken by a boat to travel 80 km with the current, if the speed of the boat in still water is 14 km/hr and the speed of the current is 6 km/hr.
Option 1: 6 hr
Option 2: 4.5 hr
Option 3: 5 hr
Option 4: 4 hr
Correct Answer: 4 hr
Solution :
Given: The speed of the boat in still water is 14 km/hr and the speed of the current is 6 km/hr.
Use the formulas,
The downstream speed = The speed of the boat + The speed of the stream,
⇒ The downstream speed = 14 + 6 = 20 km/hr
Let the time taken be
⇒
Hence, the correct answer is 4 hr.