Problem of the Week - Algebra and Up - Aug. 30 to Sept. 5, 2020

Algebra and Up:

Question: Mia has two cans of purple paint and a can of white paint. One of the cans of purple paint is 30% red and 70% blue. The other is 50% red and 50% blue. If Mia wants 8 fluid ounces of a mixture that is 20% red, 30% blue, and 50% white, how many fluid ounces of each kind of paint does she need?

Answer: 2 fluid ounces of 30% / 70%, 2 fluid ounces of 50% / 50%, and 4 fluid ounces of white

Solution: Right away, we know that we need 4 ounces of white paint because 50% of 8 ounces is 4 ounces. So, next we need to find out what amounts of the two purple paints to mix together to make 4 ounces of a 40% red, 60% blue paint (we need to double the percentages because we’re only dealing with the half that isn’t white). We can see that the average of 30% red and 50% red is 40% red, so we need equal parts of the first and second paints. That’s 2 ounces of each to make 8 ounces total. Alternatively, we could use the equation 50%(4 – x) + 30%x = 4(40%) wherein x represents the amount of the first paint.