More workers reduce the days: 20 women can complete a piece of work in 7 days. If 8 more women are added (i.e., total 28 women), in how many days will they finish the work?

Introduction / Context:
For constant-efficiency workers, total work measured in woman-days remains invariant. If the number of workers increases, the days required decrease proportionally. The product of workers and days equals the fixed total work for the job in this model.

Given Data / Assumptions:

• Total work W = (20 women) * (7 days) = 140 woman-days.
• New team size = 28 women (20 + 8 added).

Concept / Approach:
With the same type of workers, W = workers * days. Solve for days = W / workers with the new team size. No change in efficiency per worker is assumed across scenarios.

Step-by-Step Solution:

Verification / Alternative check:
If 28 women work 5 days, total = 28 * 5 = 140 woman-days, matching the original job’s workload.

Why Other Options Are Wrong:
4.5 or 5.5 days misrepresent the exact proportional decrease; 6 or 4 days also do not maintain the required woman-day total.

Common Pitfalls:
Assuming non-linear effects or changing efficiencies when the problem states identical workers. Here, proportional scaling applies directly.

Final Answer:
5 days