How to increment or decrement my price when you do +1% or -10% in flutter

I want to increment my price by the percentage that the user types in the UI, how do I do the math of that?

for example with simple math you do it like this

1. Increase the value by 1%: 1.45 x 1.01 = 1.4645
2. Decrease the value by 1%: 1.45 x 0.99 = 1.4355
3. Increase the value by 10%: 1.45 x 1.10 = 1.595
4. Decrease the value by 1%: 1.45 x 0.90 = 1.305

But I don’t know how to do it with flutter because the user is gonna put a value from 1 to 1000 in the percentage that he wants to add.

How to change that value to match the equation above?

>Solution :

If x is the percentage the user fills in the UI and y is the value, then you do:

(x / 100 + 1) × y

x is positive for increase and negative for decreasing percentage.