Add A Percentage

[springbulb81]

I know how to work out what is 20% of 119.


But what I need is how to work out what the figure was originally with 20% deducted to make it 119

Please help . What's the sum I need to do?

[Prudie]

Divide by 80 and multiply the answer by 100

[dr b]

take 119/(1-0.2) = 148.75.

[Buenchico]

To get from the 'starting figure' to 119 you work out 80% of it by multiplying by 0.8.

Therefore to reverse the operation you need to DIVIDE BY 0.8

[Nini74]

divide by 100 and multiply by 120. that's how I work out what a net figure would be with tax on top. Same goes for working out a gross figure to net, but backwards, so divide by 120 and multiply by 100 to find the net figure.

[Buenchico]

Nini74's method will add 20% of 119 onto it. That is NOT what is required (i.e. to add 20% of the unknown original figure onto 119).

I sincerely hope that Nina74 wasn't in one of the CSE/O-level/GCSE/A-level maths classes that I taught!

[ToraToraTora]

As above, with any of these things you have to work out what you did to get the figure then reverse it with standard Algebra:

eg 119 = N x 0.8 so rearrange for N
N= 119/0.8

easy!

[hc4361]

Surely multiplying the figure by 0.8 just gives 80% of 119 = 95.2

20% of 95.2 = 19.04. 95.2 +19.04 = 114.24, not 119.

[jackthehat]

X = 100%
119 = 80%

119 / 8 = 10% (= 14.875)

14.875 * 10 = 148.75 = X(100%)

[craft1948]

Divide by 8 and times by 10..............

[Buenchico]

Hc4361:
Not multiply, DIVIDE!!!