While selling rice, a dealer charges for 1500 grams but gives only 1320 grams. Calculate the gain percentage.

After comparing cost and selling values, the result is 19.64%. Profit = SP − CP, Loss = CP − SP, and the percentage is calculated on cost price. The question-specific working supplied in the record is: Gain% = ((Claimed weight − Actual weight) / Actual weight) × 100 = ((1500 − 1320) / 1320) × 100 = 13.64%. Profit and loss questions become unreliable when a percentage is applied to the wrong base. Profit or loss percent uses cost price, while discount percent uses marked price. The distractors 8.64%, 16.64%, 13.64% can result from interchanging cost price and selling price, treating discount as loss, adding successive rates, ignoring quantity, or rounding before the final step. A dependable check is to assume cost price 100 whenever only percentages are involved, reconstruct the selling value, and compare the resulting ratio with the selected option. Also verify direction: profit requires selling price above cost price, whereas loss requires it below cost price. This method preserves the numerical relationships in the stem and develops formula selection, percentage-base recognition and option elimination for SSC, Railway, Banking and other competitive aptitude examinations.