One hundred percent of which number is equal to 20?

Introduction / Context:
This is a very basic percentage question that checks whether you understand that 100 percent of a quantity simply means the entire quantity. It is useful as a warm-up and reinforces the meaning of percentage as a fraction of 100.

Given Data / Assumptions:

• We are told that 100 percent of some number equals 20.
• We must find that original number.
• All numbers are real and we expect a simple answer from the options given.

Concept / Approach:
Percent literally means per hundred. So 100 percent is 100 divided by 100, which equals 1. Multiplying any number by 1 returns the number itself. Therefore, when a question says that 100 percent of some number is 20, it means the number itself is 20. We can also express this with a simple equation using basic multiplication.

Step-by-Step Solution:
Step 1: Let the unknown number be N.Step 2: Translate the statement 100 percent of N is 20 into an equation. Since 100 percent equals 100 / 100 = 1, we have 1 * N = 20.Step 3: This simplifies directly to N = 20.Step 4: Therefore the original number is 20.

Verification / Alternative check:
Take N = 20 and compute 100 percent of N in the usual way. One hundred percent of 20 is (100 / 100) * 20 = 1 * 20 = 20. This matches the given value. No other number can satisfy the equation 1 * N = 20, so the answer is unique and verified.

Why Other Options Are Wrong:
If the number were 100, then 100 percent of it would be 100, not 20. If the number were 500, then 100 percent of it would be 500. If the number were 0, 100 percent of it would be 0. For 10, 100 percent of 10 would be 10. None of these equal 20. Only when the number itself is 20 do we get 100 percent of the number equal to 20.

Common Pitfalls:
Sometimes students confuse 100 percent with 100 or treat percent as a separate operation that changes the value in an unexpected way. Remember that 100 percent is exactly equal to 1 as a multiplier, so it does not change the value at all. Another mistake is to overthink the problem and attempt unnecessary calculations, when the direct interpretation is sufficient.

Final Answer:
The original number whose 100 percent is 20 is 20, so the correct option is 20.