[ryo23]

We need help with this problem. Let's go with the number 20 and if we add 5% the answer will be 21. OK But if we subtract 5% of 21 the answer is 19.55. Our question is how can we get back to the #20?

It might be a simple answer but we need help. Is there a formula?

VERY Confused!! :confused::confused::confused:

[ArcSine]

If u represents the percentage you originally added to the starting number (5%, in your example), then



is the percentage you'd need to deduct from the intermediate amount to get back to your original starting number.

For example, if you start by adding 25% to some starting number, then (by that formula) you'll get back to the starting number by deducting 20% from the intermediate amount.

Of course, re-express your percentage into decimal form when using the formula; i.e. u = 0.05 in your example.

Hope that helps out a bit.