I have a range 1-10. Now, I need to find the percentage increase, if the first value was 4...and the second was 9.
Do I do it like ( new_value-old_value)*100. In this case ((9-4)/4)*100=125 ? Or is there a different formula for when the range is known, in this case 1-10.?
The percentage increase from $4$ to $9$ is $125$ as you computed. Given the range you could see $4$ as $40\%$ and $9$ as $90\%$. The difference of these is $50\%$. These are two very different questions and it is not surprising that they have two different answers. You need to be clear what question you are asking.