Question 20 Suppose a boat takes 1 hour to travel 13 km in the direction of the stream and...
Reliance Industries technical mcq question, verified with a worked answer. Free to practise - no sign-up.
Question 20
Suppose a boat takes 1 hour to travel 13 km in the direction of the stream and 5 km against the direction of the stream. Find the speed of the boat in still water.
Show answer & explanation
The speed of a boat in still water is the arithmetic mean of its downstream speed and upstream speed. Given the distances covered in one hour, the downstream speed is 13 km/h and the upstream speed is 5 km/h.
Step-by-step Derivation:
Step 1: Identify the downstream speed (v_down). Since the boat travels 13 km in 1 hour, v_down = 13 km/h.
Step 2: Identify the upstream speed (v_up). Since the boat travels 5 km in 1 hour, v_up = 5 km/h.
Step 3: Use the formula for the speed of the boat in still water (u): u = (v_down + v_up) / 2.
Step 4: Substitute the values: u = (13 + 5) / 2 = 18 / 2 = 9 km/h.