Let's cut up a hexagon into 6 pieces:

hexagon          hexagon in 6 pieces

Each piece 1/6 of a hexagon is 1/6 of the hexagon. Right?

And 1/6 of a hexagon1/6 of a hexagon1/6 of a hexagon1/6 of a hexagon is 4/6 of the hexagon.

So, what if we wanted to add

1/6 + 4/6 ?

Hmm... that would be

1/6 of a hexagon + 1/6 of a hexagon1/6 of a hexagon1/6 of a hexagon1/6 of a hexagon

Count them up

= 1/6 of a hexagon 1/6 of a hexagon 1/6 of a hexagon 1/6 of a hexagon 1/6 of a hexagon =
     

So 1/6 + 4/6 = 5/6

Cool!