9514 1404 393
Answer:
45%
Explanation:
The percentage change is calculated using ...
percent change = ((new value) - (old value))/(old value) × 100%
For your numbers ...
percent change = (11 -20)/20 × 100% = -9/20 × 100% = -45%
The negative sign indicates the change is a decrease. Here, you're asked for the amount of decrease.
The percent decrease is 45%.