
#1
Mar1512, 10:32 AM

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 ((86)/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? ((21)/2)*100=50%, but it should be 100%. Can anyone help me with this problems? 



#2
Mar1512, 02:01 PM

HW Helper
Thanks
P: 4,670

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



#3
Mar1512, 02:06 PM

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.




#4
Mar1512, 02:09 PM

HW Helper
Thanks
P: 4,670

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



#5
Mar1512, 02:13 PM

Mentor
P: 21,019

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. 



#6
Mar1512, 02:29 PM

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.




#7
Mar1512, 02:29 PM

P: 232

[itex]\frac{newold}{old}[/itex](100)




#8
Mar1512, 04:00 PM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 38,886




Register to reply 
Related Discussions  
Percentage question  Precalculus Mathematics Homework  7  
Percentage Weight Question  Biology, Chemistry & Other Homework  0  
Percentage uncertainty and percentage error  Introductory Physics Homework  1  
Percentage Question  General Math  10 