The sum of three numbers is 172 . If the ratio between the first and second be 3 : 4 and that of between the second and third be 5 : 2, then find the second number.

80

   I     :      II      :      III      :    Total

   3    :       4

                 5      :        2

----------------------------------------------------------                  

  15     :       20    :       8     :     43

 43R = 172 

1R = 4 

20R = 20 × 4 = 80 

Hence , second number = 80