Foundation
USE WHEN
Final value is known after a percentage increase/decrease; original value is asked.
BEST METHOD
Equation Method
TARGET
45–60 sec
MASTERY
not started
Final value is known after a percentage increase/decrease; original value is asked.
Undo the multiplier instead of subtracting the percentage from the final value.
After +25%, divide by 1.25; after −20%, divide by 0.80.
Let original = x, build x(1±r/100)=final, then solve directly.
Timed drill
Identify the base or invariant before you calculate.
Attempt first · Standard Example
Attempt first · CAT-Level Example
3-level practice ladder
Foundation
CAT Standard
Advanced / Hybrid
reverse percentage appears inside marked-price, discount and profit questions; exact standalone mapping not asserted.