# Help with percentages..

• Feb 20th 2009, 08:01 AM
tgreaves
Help with percentages..
Suppose I have the number 1000, I take 34% away from that which leaves me with 660..

Lets say I have the 660 and I know that 34% was removed from number x to give me that 660.. Whats the formula to get the original number(1000) given the number 660 and the 34%????
• Feb 20th 2009, 08:09 AM
Quote:

Originally Posted by tgreaves
Suppose I have the number 1000, I take 34% away from that which leaves me with 660..

Lets say I have the 660 and I know that 34% was removed from number x to give me that 660.. Whats the formula to get the original number(1000) given the number 660 and the 34%????

$\displaystyle \frac{660\times 100}{x} = 34$
therefore
$\displaystyle x= \frac{660 \times 100}{34}.....formula$
• Feb 20th 2009, 10:33 AM
tgreaves
Quote:

$\displaystyle \frac{660\times 100}{x} = 34$
therefore
$\displaystyle x= \frac{660 \times 100}{34}.....formula$

I think im missing something here..

$\displaystyle \frac{660 \times 100}{34}$ does not = 1000..
• Feb 20th 2009, 11:35 AM
Air
Quote:

Originally Posted by tgreaves
Suppose I have the number 1000, I take 34% away from that which leaves me with 660..

Lets say I have the 660 and I know that 34% was removed from number x to give me that 660.. Whats the formula to get the original number(1000) given the number 660 and the 34%????

If you are told that $\displaystyle 34\%$ is reduced then you are aware of the fact that the value remaining is $\displaystyle 100\% - 34\% = 66\%$. For example, the value of reducing $\displaystyle 1000$ by $\displaystyle 34\%$ is the same as having $\displaystyle 65\%$ remaining.

Given $\displaystyle \frac{a}{b} = c\%$ where $\displaystyle a$ is the value remaining, $\displaystyle b$ is the original value and $\displaystyle c\%$ is the percentage. Therefore, with manipulation it can be deduced that $\displaystyle b = (100 \times a) / c$.

For your example, $\displaystyle b = \frac{100 \times a}{c} \rightarrow x = \frac{100 \times 660}{66}$