How it works
In the made-up town of Pebble Mill, Lio owed twenty coins on a bike pile and ten on a games pile. The bike pile adds one extra coin for every full ten owed, and the games pile adds one for every full twenty.
Lio can pay eight coins a month: one coin goes to each pile and the rest to just one of them.
The snowball pays the smallest pile first. The avalanche pays the costliest pile first.
Both plans clear both piles. One pays a few coins less and one wins sooner, and which to pick is a personal call.