Two cells of EMF 2E and E and internal resistance 2r and r respectively are connected in parallel. obtain the expression for equivalent EMF and the internal resistance of the combination

If cells are connected in parallel, 
a) Eeff:-
    E/r=E/r1+e/r2
​b)Reff:-
  1/r=1/r1+1/r2

using the above given relation u can solve ur query... :) 

first let's find the equivalent internal resistance 
1/r=1/2r+1/r=3/2r
----> r= 2r/3

now for the equivalent emf
​E/r=E1/r1+E2/r2
this implies E=r(E1/r1+E2/r2)
​therefore, on substituting the values
E=2r/3(2E/2r+e/r)
 =2r/3(2E/r)
=4E/3

hope it helps.... :)