Foundation
USE WHEN
A value changes from old to new and relative change is asked.
BEST METHOD
Multiplier Method
TARGET
45–60 sec
MASTERY
not started
A value changes from old to new and relative change is asked.
Percentage change always uses the original value as the denominator.
Use multiplier language: +x% → ×(1+x/100); −x% → ×(1−x/100).
Think old value × change factor instead of using change/original every time.
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
cat 2021 slot 2: investment loss followed by growth requires percentage-change equations across two years.