A shade of paint is made by evenly mixing m gallons of white paint, costing $12 a gallon, with n gallons of blue paint, costing $30. What is the cost, in dollars per gallon, of the resulting mixture? Select:
A) 12m +30n
B) 42(12m +30n)
C) (12m +30n)/42
D) (12m +30n)/(M+ N)
E) 42(M+ N)/(12m +30n)
M gallons of white paint and N gallons of blue paint are combined to form a new mixture. The total number of gallons in the new mixture will be M + N gallons   M gallons of white paint cost $12, so the cost of adding this mixture is 12M   N gallons of blue paint cost $30, so the cost of adding this mixture is 30N   The cost per gallon of the new mixture is equal to the total cost of all the paint used divided by the total number of gallons used to produce it:   cost of new mixture: 12M + 30N   total gallons used: M+N   cost per gallon = total cost/total gallons used = (12M + 30N)/(M+N)   ANSWER:(12m +30n)/(M+ N)
<result>D</result>
A shade of paint is made by evenly mixing m gallons of white paint, costing $12 a gallon, with n gallons of blue paint, costing $30. What is the cost, in dollars per gallon, of the resulting mixture?