A fruit seller sells 40% of his apples and still has 420 apples left. How many apples did he originally have?

Introduction / Context:
This inventory question uses percentages of a whole. Selling 40% leaves 60% in stock. Knowing the remainder, we back-calculate the original stock using division by the remaining percentage.

Given Data / Assumptions:

• Sold = 40% of original.
• Remaining = 420 apples = 60% of original.

Concept / Approach:
If R = remaining and O = original, then R = 0.60O ⇒ O = R / 0.60. Use fraction 3/5 for faster mental math: O = 420 ÷ (3/5) = 420 * (5/3).

Step-by-Step Solution:

Verification / Alternative check:
Check: 40% of 700 = 280 sold; remaining = 700 − 280 = 420, which matches.

Why Other Options Are Wrong:

• 588, 600, 672: Do not yield 420 as 60% when tested.

Common Pitfalls:
Using 40% instead of 60% for the remaining, or incorrectly converting percentages to fractions.

Final Answer: