title: math.floor(21000*0.7) returns 14699 but math.floor(14700.0) returns 14700
body: <h1>Problem</h1>
  <p>as title mentioned, when use <code>math.floor()</code> on <code>21000*0.7</code> and <code>14700.0</code> the returned value is different.</p>
  <p><code>math.floor(21000*0.7)</code> returns <code>14699</code>, but <code>math.floor(14700.0)</code> returns <code>14700</code>.</p>
  <h1>Lua versions</h1>
  <p>5.3.x and 5.4.x</p>