Add A Percentage

springbulb81 | 17:02 Sun 17th Nov 2013 | Business & Finance

10 Answers

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?

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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!