Charlie and Abi put a counter on 42. They wondered if they could visit all the other numbers on their 1-100 board, moving the counter using just these two operations: x2 and -5. What do you think?
Two Much
Age 11 to 14 Challenge Level
Explain why the arithmetic sequence
1, 14, 27, 40, ...
contains many terms of the form 222...2 where only the digit 2
appears. How many twos appear in these terms?