My son really struggled with proportion so I had to think of a way to use resources we already had in the house to help him.  Connect 4 was the most fantastic tool!  I would give him a scenario, for example: 'There are eight boys in the playground.  One in four is wearing a red jumper.  How many are wearing red jumpers?'  He would then post the coins into the slot according to the problem.  The visual element of it really helped him.  This could also be a good way to teach children multiplication (e.g.: 3 rows of 4 coins equals 12 coins altogether).