I saw this puzzle many moons ago and so I assumed it would already be on here somewhere. I have looked and not found, though, and so I present to you a puzzle that baffled me when first I saw it.
A friend gave me this riddle, stating that it would be easy for children but hard for grown-ups.
Any combination of four digits has an determined value. Here are some examples (note, the position of ...
I have been given 24 hours to solve this.
So, my friend has given me 10 examples.
$$1024 = 1$$
$$1000 = 3$$
$$2880 = 5$$
$$6591 = 2$$
$$2113 = 0$$
$$1345 = 0$$
$$1987 = 3$$
$$8888 = 8$$
$$5632 = 1$$