Exponential

Maggie needed a new mobile phone. She lost her old number as a product of the house move back to Culebrón from Cartagena. We cobbled together a solution but when her HTC phone, which she has never taken to, started to have software problems she decided it was time to get a shiny new phone and  a brand new number.

The range of offers was bewildering. Contract or pay as you go. Real or virtual networks. Household names like Vodafone and Orange or newcomers like Pepephone? Eventually the choice was made about which phone and which set up.

There was a last minute scramble when the device they used in the Yoigo shop to scan identity documents wouldn't take a British passport. The passport was much thicker than the Spanish ID cards the scanner had been designed to cope with. Maggie's Spanish ID was no good as it didn't have a photo. They managed in the end though.

The thing that surprised me was the number. Spanish mobile numbers are nine figures long and begin with 6 whilst Spanish landlines are also nine numbers long and begin with a 9. Well, that's the general wisdom.

The mobile number assigned to Maggie begins with a 7. A new series. In Cartagena our landline number began with an 8. Spaniards often thought I was having a language problem when I gave them the number. "No, fixed lines begin with a 9," they said. One chap went so far as have me phone his mobile to confirm the number. He was very apologetic.

I seem to remember that the number of combinations in a series of numbers is worked out by simple multiplication. So for a nine number sequence it would be 9 times 9 times 9 times 9 times 9 times 9 times 9 times 9 times 9 or 387,420,489 variations. The initial 6 cuts this down to 43,046,721 choices. That's a lot of numbers. On the other hand there are around 47 million people in Spain and everyone  from the eldest granny to the smallest child has a mobile so, when I think about it, I'm surprised the 6 numbers lasted so long!