Compared different unit quantities

1.Length of a pencil is 15cm and its diameter is 5mm.

What is the ratio of the length of pencil and diameter.       

The length and diameter of the pencil are given in 
different units.

The length of pencil in centimeter and the diameter    
diameter of pencil in millimeter. 

       First we convert them into same unit.

                Length of the pencil =  15cm
                                     1cm  =  10mm
                   15cm =  15 x 10  =  150mm.
                  diameter of pencil = 5mm

       now length of pencil is 150mm and diameter
       of pen is 5mm,both are in same unit. 

       The ratio of the length of pencil and diameter is
                           150:5 = 150/5 = 30/1

       The ratio of the length of pencil and diameter is
                                   30/1
                                   30:1

2.What is the ratio of 2kg mango and 500gm apple.                         
        The weight of mango and apple are given 
         in different units.

        Weight of mango, in kilo grams and weight 
         of apple in grams.

                 First we convert in same units.

                         1kg  = 1000gm 
                         2kg  = 2 x 1000 = 2000gm.

       now the weight of mango is 2000gm and weight
       of apple is 500gm, both are in same unit.

              The ratio between mango and apple is
                                 2000 : 500  
                                 2000/500
                                     4/1
              The ratio between mango and apple is
                                     4:1