Category Archives: Curriculum

The Kayaker’s Conundrum: Solutions

Kayakers on the river Adur

Many thanks to everyone who suggested solutions to this conundrum.

It would appear there are two algorithms you can can follow to solve it. Your choice of algorithm depends on whether you live near the start or finish of the paddle. Either way, you only need one bike.


Algorithm 1: If you live near the start:

  1. Drive to the start, drop the two kayaks off. One of you stays with the kayaks.
  2. The other person drives to the finish, leaves the car there, then cycles back to the start and locks up the bike.
  3. You both paddle down the river to the finish.
  4. You both load the kayaks onto the car and drive back to the start.
  5. Unlock the bike, load it onto the car, and drive home.

Algorithm 2: If you live near the finish:

  1. Drive to the finish and lock the bike up.
  2. Drive to the start and unload the kayaks.
  3. You both paddle down the river to the finish.
  4. One of you stays with the kayaks, while the other unlocks the bike, cycles back to the start and loads the bike onto the car.
  5. Drive back to the finish, load the kayaks onto the car, and drive home.

Both algorithms work, whether you live nearer the start or the finish, but choosing the wrong algorithm could result in driving twice the distance you need to. Imagine the distance (by road) between start and finish is 10km, and you live at the start. Algorithm 1 will result in 20km of driving, while algorithm 2 will result in 40km of driving. If you live at the finish, it’s the reverse.

If you live midway between start and finish it doesn’t matter which algorithm you choose. they both involve 30km of driving.

So a little logic (‘selection’ in programming speak) is required before the correct algorithm is chosen:

IF home to start < home to finish

algorithm 1


algorithm 2


The Kayaker’s Conundrum: An Exercise in Computational Thinking

20160928_181301Here’s a middle class problem that requires some computational thinking.

There are two of us, and we each have a single person kayak. We want to go for a paddle down the river. We can attach our kayaks to the top of our car, so we can drive them to the start. Trouble is, we can only paddle downstream. We can’t turn round and paddle back to the start: the current is too strong. We can attach bikes to the back of our car, so we could use them somehow. We have locks for our bikes, but not our kayaks, and don’t want to leave anything alone, unless its locked. We are not prepared to walk at any time, apart from walking the kayaks into and out of the river.

How can we best utilise our resources so we can go for a paddle and still get everything home again without having to walk anywhere?

Hint: There are a couple of algorithms you can use to solve the conundrum. But which is best? Which will involve the least amount of driving? Does it depend on where you live: close to the start or close to the finish? What if you live half way between the start and finish?

How to fix ‘Unfortunately micro:bit has stopped’ error.

Screenshot_2016-09-20-18-15-42Screenshot_2016-09-20-18-16-00J5 microbit error

A few weeks ago, keen to use my micro:bit to control my Google Nexus 5’s camera I tried to install the Samsung micro:bit app. I was a little surprised when I was told (by the app) that it wasn’t compatible with my hardware. A bit annoying I thought, but it’s Samsung’s app so I thought maybe they’ve coded it so it only works on Samsung devices.

So last week when my new Samsung Galaxy S5 arrived I was keen to try the app again. Surely it will work with Samsung’s most popular smartphone. This time there was no polite incompatibility message, the app installed in an instant. I then used the app to pair my micro:bit and S5, and after a couple of failed attempts (where I didn’t follow the instructions properly it must be said) it appeared to have paired successfully. Brilliant I thought. Now lets have some fun.

Well, unfortunately that’s where the fun ended, because every time I tried to connect to my micro:bit with the app I instantly got the message ‘Unfortunately micro:bit has stopped’. I tried un-pairing and re-pairing my devices, updating my S5, and I even updated the firmware on my micro:bit. But still the same error message.

Then I did what I should have done in the first place: I googled the error message. I didn’t get a direct hit, but I did notice a lot of people were getting remarkably similar error messages with other apps installed on the S5 (and other smartphones). This was their solution and I can confirm it fixed my micro:bit app error a treat.

  1. From the home screen, tap ‘Apps’, then ‘Settings’.
  2. Scroll down to ‘Applications’ then tap ‘Application manager’.
  3. Scroll down to, and tap micro:bit.
  4. Tap the ‘CLEAR DATA’ button, then ‘Clear’ to confirm. This should clear the cache as well.

Unfortunately, now that the micro:bit app is working on my S5, I’m sorry to report that it isn’t actually very good. Writing code is extremely fiddly and it takes forever to compile. It could be that I’m not using it properly, so I’ll persevere for now. Watch this space for a full review of the app.