Question 88741

 Three oranges cost half of what nine apples cost.  If one orange and one apple together cost 30 cents, how much does one orange cost?  
    Let the cost of 1 orange be = X  cents  and the cost of apple be = Y cents

     total cost of 1 orange &1 apple = X+Y = 30  cents........eq'n (1)

   given cost of 3 oranges = 1/2(cost of 9 apples)

                    i.e,  3X = 1/2(9Y)

                           X = 9Y/6 = 3Y/2 

      eliminate X  in eq'n (1)  by substituting  for X 


       therefore  X+Y = 30,   or  3Y/2+y = 30   

                                   3Y+2Y/2 = 30

                                    5Y/2 = 30

                                     Y = 30*2/5 = 12

             The cost  of an apple = 12 cents

  Therefore the cost of an orange = 30-12 = 18  cents