I have a head-torch with a pretty good compromise. The bay either accepts the proprietary battery, or three AAA batteries. The supplied lithium battery lasts longer than the AAA, but it's nice knowing the device will outlive the battery
The casino will break even, but for the gamblers there will be a small number that win big, and a much larger number that lose out.
Consider two rounds, there's a 25% chance you 4x your money, a 50% chance you 0.75x your money and a 25% chance you 0.25x your money
In the UK cell numbers start with 07 and landline numbers start with 01. And there is no region encoded in a cell number, but landline numbers begin with an area code.