Shortcut Trick The quantity of solid pulp remains constant during drying. Pulp in Fresh Fruit = Pulp in Dry Fruit ⇒ 28% of 100 kg = 80% of Dry Fruit ⇒ Dry Fruit = (28 × 100) ÷ 80 = 35 kg ∴ The correct answer is 35 kg. Alternate Method Given: Weight of fresh fruit = 100 kg Water in fresh fruit = 72% Water in dry fruit = 20% Formula Used: Amount of pulp = Total weight × (100 − Water %) Note: The weight of the solid pulp remains unchanged when water evaporates. Fresh Fruit (100 kg) Water 72% (72 kg) Pulp 28% (28 kg) • • Constant Pulp Weight Dry Fruit (x kg) 20% Pulp 80% (28 kg) Total Dry Fruit Weight = 28 kg ÷ 80% = 35 kg Calculations: ⇒ Percentage of pulp in fresh fruit = 100% − 72% = 28% ⇒ Weight of pulp in 100 kg fresh fruit = 28% of 100 = 28 kg ⇒ Percentage of pulp in dry fruit = 100% − 20% = 80% ⇒ Let the total weight of the dry fruit be x kg. ⇒ Since the pulp remains the same, 80% of x = 28 kg ⇒ (80 ÷ 100) × x = 28 ⇒ x = (28 × 100) ÷ 80 ⇒ x = 35 kg ∴ The correct answer is 35 kg. Related Concepts: Constancy in Mixtures (Evaporation) When a solution is heated or a fresh fruit dries, only the water content evaporates. The absolute quantity of the solid component (pulp, salt, sugar) remains constant throughout the process. Ratio Method Application Because the pulp amount is constant, the formula translates to: Pulp % in fresh × Fresh Weight = Pulp % in dry × Dry Weight. This implies that the total weight of the fruit is inversely proportional to the percentage of its constant element. Base Percentage Choice When solving evaporation or mixture problems, always identify the component that is NOT changing and immediately use it as your base reference to frame a one-line equation.