# Count On

## Explorer

#### Puzzle of the Day

These puzzles are also printed in Eight days a week, a booklet published by the Association of Teachers of Mathematics.

Start with any number less than 20. If the number is even, halve it. If the number is odd, add one. Continue using the same rules writing each number one after the other. e.g. 17, 18, 9, 10, 5, 6, 3, 4, 2, 1. Do they always end in 1? What is the longest list of numbers?

Answer: 17 is the longest