## Thursday, July 14, 2011

### A belt and braces

Today's phrase is belt and braces (for the English) or  belt and suspenders (for the Americans).

Notice our man on the left who is wearing a pair of suspenders as well as a belt on his pants. This double  approach is designed to help make sure he won't be caught with his pants down (unprepared).

How do I relate this old expression to the mathematics we unveil to elementary school kids with our Excel Math curriculum?

Our whole approach is a belt and braces design. Why? This is math education. It's a critical component of learning to participate in society, and we don't want to fail at it.

Here are our two strategies:

1. We teach kids to check their own work. When our students do a set of related problems in Excel Math, they then go on to solve a Checkanswer. This check-sum number allows them to confirm that the original group of answers were correct.

Let me show you - it's easier than trying to describe it all in words. Below, you see a box with three problems. The answers are shown in red. Once all three problems are solved, students add those three answers and compare the resulting sum (32) with the number in the box to the right of the group label H (32). If their answer does not match, they go back and recheck their work on the problems in this group.

We use this process throughout much of Excel Math - introducing it in 1st Grade and carrying it on through 6th Grade. The set above is from 4th grade; the more complicated version below is from 6th:

2. When they are working on complex problems that require a series of steps, we always ask students to try to solve them twice, in different ways. One solution is the belt, the other solution can be the braces. If they solve it twice using two varying approaches, they will never be embarrassed by their mistakes.

Of course, some people feel that a belt and braces strategy is redundant and unnecessary. It can be costly and time-consuming. It's like making a back-up flight reservation, so in case one airline is unable to fly, you can just walk over to another ticket counter.

Those people ask, Wouldn't it be better to trust one, less expensive solution?

I think it's safe to say it all depends on your point of view, and the risks that are involved ... we give our kids both belts and braces in Excel Math, and it's up to them to decide whether to wear them both or not.

Businesses are run by grown-up kids. As large companies streamline their supply chains and then get caught with their pants down due to natural disasters (Japan), political upheavals (Libya), supplier issues (Boeing 787) and so on, they begin to look around for some suspenders ...