Percent Increase and Decrease with Equations
Student Summary
We can use equations to express percent increase and percent decrease.
For example, if y is 15% more than x, we can represent this by using any of these equations:
y=x+0.15x
y=(1+0.15)x
y=1.15x
So if someone makes an investment of x dollars, and its value increases by 15% to reach $1,250, then we can write the equation 1.15x=1,250 to find the value of the initial investment.
Here is another example: if a is 7% less than b, we can represent this by using any of these equations:
a=b−0.07b
a=(1−0.07)b
a=0.93b
So if the amount of water in a tank decreased 7% from its starting value of b to its ending value of 348 gallons, then we can write 0.93b =348.
Often, an equation is the most efficient way to solve a problem involving percent increase or percent decrease.
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