# Homework Help: Question about percentage

1. Mar 15, 2012

### xeon123

I'm trying to understand this problem.

If a lollipop costed $6 and now it costs$8, how much percent the price grow?

I think the answer is ((8-6)/8)*100=25%

So I'm trying to apply this solution to the new problem. If a lollipop costed $1, and now it costs$2, how much percent the price grow?
((2-1)/2)*100=50%, but it should be 100%.

Can anyone help me with this problems?

2. Mar 15, 2012

### Ray Vickson

I think you already know the answer: what must be in the denominator in order that your second example gives you 100%?

RGV

3. Mar 15, 2012

### xeon123

In the denominator should be 1. But in the first equation it should be 8. This is the part that I don't get it. I'm putting in the denominator the current price.

4. Mar 15, 2012

### Ray Vickson

I understand what you are doing. I don't understand *why* you are doing it differently in the two examples.

RGV

5. Mar 15, 2012

### Staff: Mentor

The denominator should have the price we're calculating the percent increase/decrease for.

For your two examples, the starting prices were $6 and$1, respectively, so those are the numbers you need to use in the denominator.

On the other hand, if the price of something goes down from from $10 to$8, then the percent decrease is (10 - 8)/10 * 100 = 20 %.