It takes some bricklayers 28 hours to build a 168 m wall.How long will it take them to build a 42 m wall?

1. Break Down the Problem

To find out how long it will take to build a 42 m wall, we first need to determine the rate at which the bricklayers are working. Then we can use that rate to find the time required for the smaller wall.

2. Relevant Concepts

We will use the concept of work rate, where the rate can be calculated as: $\text{Rate} = \frac{\text{Total Work Done}}{\text{Time Taken}}$

Here, the "Total Work Done" is the length of the wall built.

3. Analysis and Detail

1. Calculate the rate of work using the given information: $\text{Rate} = \frac{168 \text{ m}}{28 \text{ hours}} = 6 \text{ m/hour}$

2. Now, we'll use this rate to determine how long it will take to build a 42 m wall: $\text{Time Required} = \frac{42 \text{ m}}{6 \text{ m/hour}} = 7 \text{ hours}$

4. Verify and Summarize

The calculated rate was consistent with the work done in the initial scenario (168 m in 28 hours). Therefore, the calculations appear to be accurate.

Final Answer

It will take them 7 hours to build a 42 m wall.