Question

In one hour , a boat goes 11 km/hr along the stream and 5 km/hr against the stream . The speed of the boat in still water ( in km/hr) is

• A. 3 km/hr
• B. 5 km/hr
• C. 8 km/hr
• D. 9 km/hr

Answer 1

Answer:

C. 8 km/hr

The speed of the boat in still water is 8 km/hr.

Clear Structure & Calculation Steps

• Downstream Speed ($D$): 11 km/hr (along the stream)

• Upstream Speed ($U$): 5 km/hr (against the stream)

Formula:

$\text{Speed of boat in still water} = \frac{\text{Downstream Speed} + \text{Upstream Speed}}{2}$

$\text{Speed} = \frac{11 + 5}{2} = \frac{16}{2} = \mathbf{8 \text{ km/hr}}$