title: Check if a given number is a multiple of another number that is a decimal
body: <p>First of all I'm not sure if &quot;multiple&quot; is the right term to use in my question. But here is my situation. I am building a shop that accepts orders by quarters of 1/4(.25) or 1/2(.5), like buying 1.5kg of rice or 1/4kg of garlic, etc. Now, when someone places an order, how do I correctly check if the quantity that he input is a multiple of that quarter.</p>
  <p>So, for example I only accept orders by 1/4 (.25 in decimal), the input and result should be the ff:</p>
  <p>.5 (good)</p>
  <p>.75 (good)</p>
  <p>1.25 (good)</p>
  <p>.8 (bad)</p>
  <p>1.33 (bad)</p>
  <p>Right now, I just divide the input by the quarter. Then, if the answer is a whole number, it's considered good.</p>
  <p>Is it the right way to do it?</p>
  <p>Thanks!</p>