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Dec

Miles Per Gallon Calculator

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Copy and paste the function into the document head. Copy and paste the form into the document body.

function calcMPG()
{
    var startMiles = document.forms[0].startingMileage.value;
    var endMiles = document.forms[0].endingMileage.value;
    var gallons = document.forms[0].gallonsUsed.value;

    if(isNaN(startMiles) || isNaN(endMiles) || isNaN(gallons))
    {
    window.alert("Each textbox must contain only numbers!");
    }
    else
    {
        if(gallons > 0)
        {
        document.forms[0].milesPerGallon.value = ((endMiles - startMiles)/gallons).toFixed(1);
        }
    }
}

<body>
<script type="text/javascript">
document.write("<p><h2>Miles Per Gallon Calculator</h2></p>");
document.write("<p><h5>To find miles per gallon, enter starting and ending mileage and gallons of gas used.</h5></p>");
</script>
    <form action ="">
        <p>Starting Miles:<br />
        <input type = "text" name = "startingMileage" value = "0" size = "10" onchange = "calcMPG()" /></p>
        <p>Ending Miles:<br />
        <input type = "text" name = "endingMileage" value = "0" size = "10" onchange = "calcMPG()" /></p>
        <p>Gallons Used:<br />
        <input type = "text" name = "gallonsUsed" value = "0" size = "10" onchange = "calcMPG()" /></p>
        <p>Miles Per Gallon:<br />
        <input type = "text" name = "milesPerGallon" value = "0" size = "10" /></p>
    </form>
</body>

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