title: Calculation using expr in shell
body: <p>I have used the following code to Calculate simple intrest and its working fine</p>
  
  <blockquote>
    <p>intrest=$(( $p * $r * $t / 100 ))</p>
  </blockquote>
  
  <p>However when i try to solve the above using <code>expr</code> it gives me error <code>expr: syntax error
  </code></p>
  
  <blockquote>
    <p>intrest=`expr $p * $r * $t / 100`</p>
  </blockquote>