The value of a company stock drops from Rs. 25 per share to Rs. 21 per share. What is the percentage decrease per share?

Introduction / Context:
This is a simple percentage decrease question in a financial context. It checks whether the learner can calculate the percentage drop in price when the old and new prices are given.

Given Data / Assumptions:

• Initial price per share = Rs. 25.
• New price per share = Rs. 21.
• We must find the percentage decrease.

Concept / Approach:
Percentage decrease is calculated as (decrease / original value) * 100. Here the original value is the initial stock price of Rs. 25 and the decrease is the difference between the initial and new prices.

Step-by-Step Solution:
Original price = 25.New price = 21.Decrease = 25 - 21 = 4.Percentage decrease = (4 / 25) * 100.Compute 4 / 25 = 0.16.So percentage decrease = 0.16 * 100 = 16 percent.

Verification / Alternative check:
If the stock price had decreased by 10 percent, the new price would be 22.50, and if it had decreased by 20 percent, it would be 20. A 16 percent decrease lies between these values and more exactly gives 25 - 0.16 * 25 = 21, confirming the accuracy.

Why Other Options Are Wrong:
4 percent, 8 percent and 12 percent do not produce a new price of 21 when applied to 25. For example, 10 percent decrease would yield 22.5, not 21. Only a 16 percent decrease matches the provided numbers.

Common Pitfalls:
Sometimes students accidentally divide by the new price instead of the old one or mistakenly treat the absolute decrease as a percentage directly. Always use the original value as the base for percentage decrease calculations.

Final Answer:
The percentage decrease in the stock price is 16 percent.