We had our Linear Systems test this morning. In my period 2 class there was quite a bit of extra time for some people (we had a 15 minute presentation in the period 1 class), so I put the following three questions on the board. If you solve them all and email me a solution (answers along with how you got them!) then I’ll have a delicious treat for you in a few days.

- How many numbers between 1000 and 9999 have no repeating consecutive digits?
*(e.g. 7225 is not allowed, but 7252 is)* - How many numbers between 1000 and 9999 have no zeros?
- How many numbers between 1000 and 9999 have exactly one zero?

These are optional, if that wasn’t already clear :)