Adding with papercraft numbers

Adding with papercraft numbers

One plus three One plus three.

Yes One plus three equals four, I think Try it Four! Great! And if you now add 2 more? 1 plus 3 plus 4.

err.

1 plus 3 plus 2? Then.

what is the result then? Now there's nothing in my way.

No.

oh yes! What number is it? Hmm.

if you take it like this? Then it's a 6.

– Exactly! 1 plus 2 plus 3 equals 6! [The older sister chimes in]: Ah, I thought 9.

Source: Youtube