I’ve always liked numbers. Perhaps it is due to a maths teacher I had when I was ten-years-old who taught us tricks with numbers. I delighted in learning that all numbers divisible by 3, when added together, make 3, 6 or 9, and numbers divisible by nine, when added together, always equal nine.  He built my confidence in adding, subtracting, multiplying and dividing. He set us entertaining puzzles like: “If it takes three men three days to dig three trenches, how many psychologists does it take to change a lightbulb?” (I think I haven’t remembered the challenge correctly! The answer, anyway, is one, but the lightbulb must really want to change. Sorry about that).