<div class="container">
<h2>Calculadora <b>poco científica</b></h2>
<input type="text" class="form-control" id="num1" value="4">
<input class="btn btn-info boton" type="button" id="suma" value="+">
<input class="btn btn-info boton" type="button" id="resta" value="-">
<input class="btn btn-info boton" type="button" id="multi" value="*">
<input class="btn btn-info boton" type="button" id="divi" value="/">
<input class="btn btn-info" type="button" id="reset" value="Borrar campos">
<input type="text" class="form-control" id="num2" value="5">
<h3>=</h3>
<input type="text" class="form-control" id="res">
</div>
$(function () {
$(".boton").click(function () {
var n1 = Number($('#num1').val());
var n2 = Number($('#num2').val());
var operacion = $(this).val();
$('#res').val(eval(n1 + operacion + n2));
$('#res').after("<p>"+n1 + " " + operacion + " " +
n2 + " = " + $('#res').val()+"</p>");
});
$("#reset").click(function () {
$(':text').val("");
});
});