1tin of 500ml blue paint costs $11.50. to finish a bedroom i need 4litre of blue paint. how much wi this cost me.

We know that 1 litre is equal to 1000ml (double the amount they're giving us), so 1 litre of paint is going to be $23 (we know this by multiplying 11.50 • 2).

Knowing this, all we need to do is multiply $23 • 4  which should give us $92.

So, the total of how much you will need to pay in this scenario to paint a room is $92 for 4 litres of blue paint.

Good luck!