Basic math question? help!?

Question

so i'm not good at figuring out percentages, and i've been racking my brain for more than half an hour, and don't wanna give up, so please help:

1. when the value of something drops from $13.90 to $12.90, what is the percentage drop?

2. when the value of something goes up from $3.50 to $4.25, what is its percentage increase?

Please, help, explain to me how to do it, thanks!!!!!!

Answer 1

1. subtract 13.90 from 12.90 and u get 1 which  means its a 1 dollar decrease so u divide 1 from the original price and u get 1/13.90 = .0719 making the precentage 7.2% to rounnd

2. subract 3.50 from 4.25 and you get a .75 cent increase. so you would divide .75 by the original price.   .75/3.50 = .2142 making the percentage 21.4%

Answer 2

$13.90 is the value at 100%. $12.90 is the value at what percent.

13.90/100 times 12.90/x. Cross multiply.

So 12.90 is 92.8 percent of  13.9. Just subtract 92.8 from 100.

Answer 3

1. percentage drop = 1/13.9*100

2. 0.75/3.5*100