"Reverse" Percentages

[jonny707]

I'm not sure it reverse is the right term but my brother is doing these for his homework and relied on me for help, unfortunately I forgot about how to do these. Is there a formula to work them out, I'm sure there is?

e.g 75% of x = 36
Find x

[ChuckFickens]

(36 / 75) * 100 = 48

[bibblebub]

75% of x = 36
i.e. 0.75x = 36

divide both sides by 0.75:

0.75x/0.75 = 36/0.75
i.e. x = 36/0.75 = 48

[chelle7272]

Ther's probably a simpler way but if you divide 36 by 75 then multiply by 100 that should get you there?

[chelle7272]

there you go knew somone could explain it better!

[jonny707]

Thank you everyone!

[factor-fiction]

No need to remember a formula.
Just scale the figures up or down as necessary
Take your example:
if 75% of x = 36 then divide by 3 to get 25%. So 25% of x is 12 . Then multiply by 4 to get 100%. 100% =48

[KARL]

75% of something is the same as the original figure multiplied by 0.75. Thus to get to the original figure you apply the inverse - you divide by 0.75. Take a less obvious number: 48% of the mystery figure is 447.36. Divide 447.36 by 0.48 and you get the original figure of 932.

[ChuckFickens]

Factor

67% of x = 29
using your method Find x

[factor-fiction]

Easy, chuck.
1% is 29/67.
So 100% is 2900/67=43.28

The point I'm making is that people often try to remember a formula (and often misremember it) when it's often better to use a 'common sense' method

[rojash]

"1% is 29/67.
So 100% is 2900/67=43.28"

You seem to have missed a step there:
1% is 29/67.
so 100% is 29/67*100

Oh, but that's we we came in :-)