Question

orange and pineapple juice are mixed in a ratio of 4 to 5 ,how much of each juice is needed to make 36 gallons of oranges-pineapple juice

Answer 1

4+5 is 9 and 36x9 is 324 because,
+5
   36
     9
 -------
  324

Answer 2

4 think of each as gallons 4+5= 9. 9x 4 = 36