Sunday Times Teaser 2666 – Multiple Calls

by Ian Duff

The 100 people in my office each have a two digit phone number from 00 to 99. My phone was recently rewired in error so that each numeric button now produces an incorrect digit.

In trying to phone four colleagues, I phoned double the intended number. For more than ten colleagues, using their number resulted in phoning three times the intended number.

Also if I tried to phone any colleague and then asked for their phone number, and then phoned their number and asked for their number, and so on … , it always took ten calls to phone the person I intended to call in the first place.

What numbers would I actually get if I key in the numbers 01, 23, 45, 67 and 89?