A seller computes profit on selling price instead of cost price. By selling an article for Rs 280, he reports a profit of 14 2/7% (on SP). Find his actual profit percentage on cost.

Introduction:
Reporting profit on selling price (SP) understates the base; converting the stated figure into an actual rupee profit and then dividing by true cost yields the correct profit percentage on cost price (CP).

Given Data / Assumptions:

• SP = Rs 280
• Reported profit% on SP = 14 2/7% = 100/7% ≈ 14.2857%

Concept / Approach:
Profit (rupees) = (reported% of SP). Actual CP = SP − profit. Then Actual Profit% = profit / CP * 100.

Step-by-Step Solution:
Profit (rupees) = (100/7)% of 280 = (1/7) * 280 = 40Actual CP = 280 − 40 = 240Actual Profit% = 40 / 240 * 100 = 16.666...%

Verification / Alternative check:
If profit were computed on CP: 16.66% of 240 is 40, bringing SP to 280 (consistent).

Why Other Options Are Wrong:
20%/25% overstate; 12.5% understates.

Common Pitfalls:
Applying 14 2/7% on CP by mistake; mixing up the definition of base.

Final Answer:
16.66 %