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# Calculations Watch

From this we see that when working out a percentage increase, you just do the difference between the final amount and the initial amount/initial amount X 100.

In this question I did the same thing. Here's my working out:

(80/300) X 100
=26.7% increase

But this is wrong. The correct answer is

(80/1,000,000) X 100
=0.008% increase

The thing I don't understand is why they do not divide by the inital amount of 300ppm. Can someone explain this to me please?

Thanks
2. (Original post by krisshP)

From this we see that when working out a percentage increase, you just do the difference between the final amount and the initial amount/initial amount X 100.

In this question I did the same thing. Here's my working out:

(80/300) X 100
=26.7% increase

But this is wrong. The correct answer is

(80/1,000,000) X 100
=0.008% increase

The thing I don't understand is why they do not divide by the inital amount of 300ppm. Can someone explain this to me please?

Thanks
If you are calculating the increase the units do not matter.

The value goes from 300 to 380, this is an increase of 80 parts in 300

= 100 x 80/300 %

Whatever the units used, the calculation would be the same ...
3. (Original post by charco)
If you are calculating the increase the units do not matter.

The value goes from 300 to 380, this is an increase of 80 parts in 300

= 100 x 80/300 %

Whatever the units used, the calculation would be the same ...
That's what I did and I still got it wrong. I'm still confused
4. Ignore my post now.

I get it.
5. I just had to read the question more carefully. I thought it was talking about the percentage increase in concentration instead of the increase in the percentage of concentration.

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