There are 150 oranges, apples and pears in a box. The ratio of the number of oranges to the number of apples is 3:5 and the ratio of the number of pears to the number of apples is 2:5. Find the number of pears in the box.

  Pears:  30

Step-by-step explanation:

Constant:

  3x + 5x + 2x = 150

                 10x = 150

                    x = 15  

Multiply ratio with constant from above:

  oranges : apples

       3 * 15 : 5 * 15

            45 : 75       ==>               45 oranges: 75 apples

  pears : apples

   2 * 15 : 5 * 15

        30 : 75          ==>                    30 pears: 75 apples

Check:

45 oranges + 75 apples + 30 pears = 150 fruits