simple math for variable

this is a real basic but I'm struggling to see why this is not working

I am trying to set a variable as a percentage in order to show a progress bar 

 but the below returns p1 & p2 as 0 (delta is a positive number)
  delta = (tidesData[14] - tidesData[13]) /60;
            p1 = (75 / 100) * delta ;
            p2 = (25 / 100) * delta;
what is the correct syntax within monkeyc to do this math?
However,  this does return a result
p1 = (100/4) * delta ;