Gina mixed paint to make her favorite shade of purple. She filled up one third of the container with red paint. Then she filled the remaining space with 4 liters of blue paint. How many milliliters of paint did Gina mix?

There is 1000 milliliters in a liter. So we're gonna work with thirds. One third is already filled, so that means two thirds is not. So 4 liters fills up 2/3 which we can infer that 2 liters fills up one third of the area ... so there is 6 liters in total. Which means there is a total of 6000 milliliters of paint.