by xeon123
Tags: percentage
 P: 81 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?
 HW Helper Thanks P: 4,676 I think you already know the answer: what must be in the denominator in order that your second example gives you 100%? RGV
 P: 81 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.
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P: 4,676

 Mentor P: 21,067 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 %. If the price happened to go back up by $2, then the percent increase would be (10 - 8)/8 * 100 = 25%. The reason we're getting a different number is we're using a different base or starting point.  P: 81 I wasn't understanding the problem because I got different percentage values. In the example of Mark44 the same price decreased 20% to pass from$10 to $8, and the increased 25% to pass from$8 to $10. Projecting my question with Mark 44 explanation, my confusion was in the different percentage values. I was thinking why a price decreases 20%, and it has to increase 25%, and not 20%, to get to the initial value? Now, I understand. P: 232 $\frac{new-old}{old}$(100)  Quote by xeon123 I wasn't understanding the problem because I got different percentage values. In the example of Mark44 the same price decreased 20% to pass from$10 to $8, and the increased 25% to pass from$8 to $10. Projecting my question with Mark 44 explanation, my confusion was in the different percentage values. I was thinking why a price decreases 20%, and it has to increase 25%, and not 20%, to get to the initial value? Because the amount you're multiplying the percent by is smaller. Math Emeritus Sci Advisor Thanks PF Gold P: 38,899  Quote by xeon123 In the denominator should be 1. But in the first equation it should be 8. This is the part that I don't get it. I'm putting in the denominator the current price. That's because the answer you gave to the first problem is wrong. If the lollypop increased from 6$ to 8$then it increased by$2 and that is 2/6= 1/3 of the original price. The price of the lollypop increased by 1/3 or 33 and 1/3 percent, NOT 25%.