Avoid base-value mistakes, reverse comparisons, and careless conversions.
What to focus on
- Always identify the original value before using increase or decrease formula.
- Do not confuse 20% of x with x is 20% more than something.
Quick formula / idea
- Base value matters more than the visible final number.
A fall from 100 to 80 is a 20% decrease, but a rise from 80 to 100 is a 25% increase.
Practice prompts
- Explain why a 20% decrease followed by 20% increase is not zero net change.
- Find the net effect.