The sum of three numbers is 105. If the ratio between the first and second be 2 : 3 and that of between the second and third be 4 : 5, then find the second number.

36

   I     :      II      :      III      :    Total

   2    :       3

                 4      :        5                  

  8     :       12    :       15     :     35

                  ↓                             ↓ × 3

                  ↓ × 3                     105 (given)

                 36