# percentages and reversing them

• Dec 10th 2007, 10:49 AM
benhathaway
percentages and reversing them
hi,
how can i do this...

i did this...

10x0.8=8

then to reverse it i tied this

8x1.2=9.6

so how can i undo both of these to get back to 10?

thanks :)
• Dec 10th 2007, 10:54 AM
earboth
Quote:

Originally Posted by benhathaway
hi,
how can i do this...

i did this...

10x0.8=8

then to reverse it i tied this

8x1.2=9.6

so how can i undo both of these to get back to 10?

thanks :)

Hello,

the reciprocal value of 0.8 is 1.25:

$\displaystyle \frac{1}{0.8} = 1.25$

and

$\displaystyle 8 \cdot 1.25 = 10$
• Dec 10th 2007, 11:15 AM
benhathaway
this is for a shopping cart and i reduced all my items by 20% using the price x 0.8. Then i tried to make it back up by doing this price x 1.2. But this didnt work so how can get the original price back?
• Dec 10th 2007, 11:25 AM
colby2152
Quote:

Originally Posted by benhathaway
this is for a shopping cart and i reduced all my items by 20% using the price x 0.8. Then i tried to make it back up by doing this price x 1.2. But this didnt work so how can get the original price back?

As earboth showed, you must multiply it by 1.25 (1 / 0.8)
• Dec 10th 2007, 12:45 PM
benhathaway
hi,
the only problem is that i have the price that has allready been discounted by 20% and multiplied by 1.2. This cannot be reversed! Now i have tried to multiply by 1.25 so i need to reverse this...

price x 0.8 x 1.2 x 1.25

Thanks :)
• Dec 10th 2007, 06:03 PM
colby2152
Quote:

Originally Posted by benhathaway
hi,
the only problem is that i have the price that has allready been discounted by 20% and multiplied by 1.2. This cannot be reversed! Now i have tried to multiply by 1.25 so i need to reverse this...

price x 0.8 x 1.2 x 1.25

Thanks :)

You want the price back to normal?

.8*1.2*1.25*y = 1
1.2y=1
y=.8333 OR 5/6