1. ## Help on Pecentages

Hi,

I am looking for an easy formula to calculate the following ;

There are several different fees for room bookings depending on time of year and room type.

Tourist information take 10% of any fee from a successfull booking

So, say the normal price for a room is £30 then I need to increase the room booking fee by the same amount that would give me £30 once the tourist information have taken their 10% fee.

This seemed easy at first but then seemed to get harder once I tried to come up with a general formula

30 + 10%
30 + (0.1 * 30)
30 + (3)
33

However if I charge 33 and tourist info take 10% thats

33 - (33 x 0.1) = 33 - 3.3 = 29.70

Somehow I lose 30p ?

I have to factor in the 10% of the 10% ???

Anyhelp appreciated!

2. First off: When you are adding 10% to the £30 you are getting 99% of the price, because £30 is only 90% of the full price, and 10% of 90% = 9%. 90% + 9% = 99%. That is why you are slightly off target!

(1) You need to first say that £30 is 90%, as it is. When you receive your £30, you are only receiving 90% of the money, because the Tourist Information took 10%.

(2) So you need to find and add an extra 10%, which you would do by diving the 90% by 9 as 90/9 = 10%. So £30 divided by 9 is 30/9, which is simplified to 10/3, which is 3.333333333....recurring.

(3) Simply add this to your £30 and get £33.33. Now when you remove 10% you will remove 3.3333... and have your 90% again which is £30.

3. Thanks alot. As usual its the way you think about the problem that trips you up !!!