[Rise]

GonzoT, первая часть:

<form name="f" style="text-align:center">
	<input type="radio" name="r" value="10,20">
	<input type="radio" name="r" value="30,40">
	<input type="radio" name="r" value="50,60"><br>
	<input type="text" name="x" value="0">
	<input type="text" name="y" value="0" readonly>
	<input type="text" name="z" value="0" readonly><br>
	<input type="text" name="sum" value="0" readonly>
</form>
<script>
document.f.onclick = document.f.onkeyup = function(){
	for (var i = 0; i < this.r.length; i++) {
		if (this.r[i].checked) {
			var v = this.r[i].value.split(',');
			this.y.value = v[0];
			this.z.value = v[1];
			break;
		}
	}
	this.sum.value = this.x.value * this.y.value * this.z.value;
};
</script>

Остальное сам