# Letters

Issue 6
in
September 1998

## Why stop?

The PASS Maths "magazine" is great! Why did publishing stop with the May '98 issue?

Jon Revelos

It didn't, PASS Maths is still going strong. We publish once per term: January, May and September. A new editorial team will be publishing the January 1999 issue, see "Time to change" in the issue 7 Editorial.

## Probabilities

I would like to know how many chances there are of guessing a number with four digits.

My cousin says that there are one in ten thousand chances of guessing, but I think that there is much more. Can you give me the answer?

F. Ferretti

Your cousin is right if you include all four-digit sequences from 0000-9999. If he/she chooses one of them at random then the chances of you guessing which one was chosen first time is 1 in 10000. That is because there are 10000 equally likely possibilities and only one of them is the right one!

If you do not allow numbers with leading 0s, the normal meaning of "four digit numbers", then there are only 9000 equally likely possibilities: 1000-9999 and the chances are therefore 1 in 9000.

## PASS Maths new look

The outlook of the site has improved. More interesting puzzle problems could be put in.

Michael Deutschemann