Whilst supervising DofE bronze practice at the weekend, I was dismayed by the inability of participants to do simple mental arithmetic. They're taught to estimate their speed at about 3kmh (yes, it's slow, but it's about right for these groups...), so they're told to allow 20 minutes per kilometre.

We tell them to measure the length of the microleg with the appropriate compass romer (and it's a challenge to get them to use the right one...), and then convert that into the number of minutes they should have to walk until they get to their next decision point or navigation feature. But they all struggled to do even the simplest of mental arithmetic; 0.3 times 20 proved very difficult, and even 0.2 times 20 produced a variety of results before they finally settled on 4.

I guess this is a consequence of over-reliance on a calculator, and the deprecation of the use of rote learning of the times table, but it's a problem.

So, whilst trying to explain this, it suddenly struck me that, if they stick to their 3kmh, 20 minutes per km estimate, each tick of the romer scale is 2 minutes. This they could cope with...

I know it's a pathetically simple technique, and would have to be scaled for faster walkers, but it actually seemed to work for the groups I was with. I'm sure it's been used before, but I don't recall reading about it.

Oh, and the other problem is them not wearing watches; again, technology means they use their phones to tell the time...

ps. the first time I encounter the groups is during supervision; I don't get to do any instruction prior to their expedition...