If a boat can have a speed of 4 km/hr in still water, for what values of speed of river flow, it can be managed to row boat right across the river, without any drift ?

Options

A. greater than or equal to 4 km/hr
B. greater than zero but less than 4 km/hr
C. only 4 km /hr
D. None of these

Explanation

To solve the problem, we need to determine the values of the speed of river flow (Vr) for which a boat can be rowed directly across a river without any drift. The boat has a speed of 4 km/hr in still water.

### Step-by-Step Solution:

1. **Understanding the Problem**:
- The boat's speed in still water is given as 4 km/hr.
- We want to find the range of river flow speeds (Vr) that allows the boat to move directly across the river without drifting downstream.

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