Question

A is one and half times as good a workman as B and together they finish a work in 12 days.in how many days can B alone do it?

Answer 1

b will take 30 days.... hope it was helpful..... though kvnmurthy has given better answer

Answer 2

Let B complete the work in X days.
productivity of B =  1/X  amount per day.
productivity of A = 3 / 2X   amount per day.

Productivity of A and B together is  5 / 2X  amount per day.

   So A and B together can finish the work in  2X / 5 days
    
     2 X / 5 = 12 days
             X = 30 days.