How is PPI calculated? What divided by what?

How is PPI calculated? What divided by what?


If it's pixel per inch, you're like a prime divided by length (in inches)



How to divide 32 by 125
How to calculate 32 △ 125


32÷125 =(32×8)÷(125×8) =256÷1000 =0.256



When doing a calculation problem in the exam, Xiao careless multiplies a number by 9, makes a mistake and divides it by 9. Then he adds 30 and makes a mistake and subtracts 30. The result is 18
The result is ()


3918



A simple algorithm of dividing 450 by 45


450/45=10*45/45=10