Fern the Hedgehog must cross the river —
but each stone holds a number puzzle.
Solve it one step at a time:
first choose which step comes first,
then work out its answer. The puzzle shrinks until one number is left!
Out of acorns — shake off the water
and try this crossing again.
One more secret: the truly viral version is written 8 ÷ 2(2+2) — with the × sign hidden. That's why adults argue about it: some read 16, some read 1. It isn't a hard sum, it's lazy writing. Good mathematicians use brackets so there is nothing to argue about — and now, so do you.