To solve this problem, we can use the concept of work rate. Here's the step-by-step process:

1. Total work done by 35 workers:

   • 35 workers take 16 days to build the house.
   • The amount of work done (in worker-days) is $35 \times 16 = 560 \text{ worker-days}$.

2. Work rate of 1 worker:

   • If 35 workers take 16 days to finish the work, the work rate of 1 worker is $\frac{1}{560} \text{ of the house per day}$.

3. Work done by 28 workers:

   • Now, we need to find out how many days 28 workers will take to complete the same amount of work.
   • Let the number of days be $x$.
   • The total work done by 28 workers in $x$ days is $28 \times x$.

4. Set up the equation: Since the total work done by both groups should be the same: $28 \times x = 560$ Solve for $x$: $x = \frac{560}{28} = 20$

Thus, 28 workers will take 20 days to build the house.

Would you like a detailed breakdown or any clarification?

Here are 5 related questions to think about:

1. What if 40 workers worked at the same rate? How long would they take to finish the house?
2. How long would it take for just 1 worker to build the house alone?
3. If the number of workers changes halfway through the project, how do we calculate the total time?
4. How does this problem change if the workers are not equally efficient?
5. What if the house size increases by 50%? How does the number of worker-days change?

Tip: Always check if the rate of work remains constant when solving these types of problems.