Question

A man riding on a bicycle at a speed of 21 km/h crosses a bridge in 6 minutes. Find the length of the bridge?

• A. 5.1 km
• B. 4.5 km
• C. 2.1 km
• D. 6.1 km

Answer 1

Answer:

C. 2.1 km

The length of the bridge is 2,100 metres (or 2.1 kilometres)

• Speed: 21 km/h

• Time: 6 minutes

Step 1: Convert time from minutes to hours
$\text{Time} = \frac{6}{60}\text{ hours} = \frac{1}{10}\text{ hours} = 0.1\text{ hours}$

Step 2: Calculate the distance (Length of the bridge)
$\text{Distance} = \text{Speed} \times \text{Time}$
$\text{Distance} = 21\text{ km/h} \times 0.1\text{ hours} = 2.1\text{ km}$