Answer: 60% decrease
Step-by-step explanation:
How to calculate percentage decrease:
Subtract starting value minus final value
Divide that amount by the absolute value of the starting value
Multiply by 100 to get percent decrease
If the percentage is negative, it means there was an increase and not an decrease.
Percentage Decrease Formula
You can use the percentage decrease formula for any percent decrease calculation:
Percentage Decrease=Starting Value−Final Value|Starting Value|×100
Example Problem: Percentage Decrease
You have a lamp with a 60-watt traditional light bulb. Your lamp uses 60 watts of electricity per hour. You're considering replacing the bulb with an LED light bulb that uses 8 watts of electricity per hour. What is the percentage decrease in the lamp's hourly energy use if you switch to an LED light bulb?
Percentage Decrease = [ (Starting Value - Final Value) / |Starting Value| ] × 100
60 - 8 = 52
52 / 60 = 0.8667
0.8667 × 100 = 86.67%
So if you switch to an LED light bulb your lamp will use 86.67% less energy per hour.
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