Dear Nelly,
Actually, percentage change mostly fits between two numbers. There is no specific formula to calculate percentage change among multiple numbers. Rather, when we face percentage change calculation, it means we are simply asked for the percentage change between the first number and the last number. In this case, the formula is.
=((Final Value – Initial Value)/Initial Value)*100
As your teacher has given you 10 different columns of values, you can calculate percentage change for each 2 individual columns and finally find a mean value of percentage change.
This is like.
=((2nd Value – First Value)/First Value)*100
Then,
=((3rd Value – 2nd Value)/2nd Value)*100
Similarly, following the same formula find all the individual percentage change. For 10 columns you will find 9 individual percentage change.
Finally, to find the mean.
=(Percentage Change of (Step 1 + Step 2 + …….+ Step 9))/ 9

Similarly, this statement is true for calculating count.

Regards,
Towhid
Excel & VBA Content Developer
ExcelDemy

Dear William Moloney,
As far as I understand, you are able to use “Format Cell” but can’t get the procedure of using “Control Panel” to fix negative number format, right?
You are using Windows 10 and you can do it easily in Windows 10.
Firstly, go to “Control Panel”.
Secondly, click on “Change date, time and number format” in the option “Clock and Region”.
Thirdly, a window named “Region” will appear. Go to “Formats” option of that window. Click on “Additional settings” at the right-bottom side of the window.
You will see a “Customize Format” window. Go to “Numbers” of this window. You’ll see many options available in this “Numbers” option.
Fourthly, in the “Negative Number Format” option, click on the value and you will see different options such as 1.1, -1.1, 1.1- etc. You need to select 1.1 here and then click OK. This is the most important step here to select 1.1. Windows 10 has default selection 0f -1.1, you need to just change it to 1.1.
Hope, your problem will be solved now. Thank you.

Regards,
Towhid
Excel & VBA Content Expert
ExcelDemy

Hello NK,
It’s awesome that you have found another solution which is applicable by adding a simple symbol in the formula you have mentioned. Yes obviously it is possible to remove blank from lists using the combination of UNIQUE and FILTER functions. The formula should be for the dataset of this article.
=UNIQUE(FILTER(B5:B14,B5:B14<>“”))
You need to add the symbol <> extra.
Here, the FILTER function is used to remove any blank values from the data.
The <> symbol is a logical operator that means does not equal.
The filtered data is returned directly to the UNIQUE function as the array argument. The UNIQUE function then removes duplicates and return the final array.

Thanks with Regards,
Towhid
Excel & VBA Content Developer