This is very cool widget. Most importantly, very useful.

Re: 1 + 2 * 3 = 9
This is NOT correct. Basic grade-level mathematics teaches that the multiplication is to be evaluated before the addition. To make it equal 9, it expressed as (1 + 2) * 3. Yes, this is more difficult to enter into a calculator, but requires the user to understand and properly re-construct the expression, which is why maths is still taught, rather than leaning purely on calculators.

This is a universal mathematical convention. Any properly functioning calculator (including the …one built into Mac OS X 10.3 and 10.4) will see the user press the "x" button and delay evaluation until the rest of the equation is entered.

http://www.eduplace.com/math/mathsteps/4/a/index.html (Grade 4 maths)
http://mathforum.org/library/drmath/view/58237.html
http://www.homeschoolmath.net/ebooks/contents_m1.php
.......
(Just google for "multiplication before addition".) More

I tried twice to download this and got a virus warning. Just thought you should know.

About Simon and the "correct" order of operations:

In your expression

1 + 2 * 3 = 7

You are using programming languages and electronic spreadsheet programs precedence scheme to perform the multiplication before the addition. In other words, you first multiplies 2 by 3, and then adds that result to 1 for a result of 7.

That may not be the way you want this expression to evaluate. Perhaps your intention was for the 1 and 2 to be added together first and that sum to be multiplied by 3…, which is the "natural" order of precedence from left to right.

As you can see in ANY desktop electronic calculator, the result of your expression using the "natural" order of precedence, should be 9.

Thus, te correct evaluation of your expression is:

1 + 2 * 3 = 9 More

Very good setup, but it needs correct order of operations:

1 + 2 * 3 = 7, not 9