Twenty men can build a 56 m long wall in 6 days (all else same). At the same rate, what length of a similar wall will 70 men build in 3 days?

Introduction:
Output for similar work is directly proportional to the product “men × days” when all work at the same constant efficiency. We can scale the known length by the ratio of (men × days) between the two scenarios to obtain the new length.

Given Data / Assumptions:

• Baseline: 20 men → 56 m in 6 days.
• New scenario: 70 men working for 3 days.
• Quality and width identical (length is the variable).

Concept / Approach:
Length ∝ (men × days). Thus, L2 = L1 * (men2 × days2)/(men1 × days1). Plug values and simplify to get an exact length in meters without intermediate rounding.

Step-by-Step Solution:

Verification / Alternative check:
Compute per man-day productivity: 56 / (20*6) = 56/120 = 0.4667 m per man-day. For 70 men and 3 days: 70*3 = 210 man-days → 210*0.4667 ≈ 98 m, confirming.

Why Other Options Are Wrong:
85, 100, 48, or 112 m do not respect the exact proportional scaling from the given baseline.

Common Pitfalls:
Mixing up direct and inverse proportions. Length increases with both men and days here (direct proportion), since total work rises.

Final Answer:
98 m