Let total work to be done = L.C.M.(20,30,24) = 120 units Let efficiency of Raja, Kundan and Mahesh be x,y,z respectively. Raja and Kundan together can build the wall in 20 days, ⇒ x+y=
120
20
=6units/day ----------(i) Similarly, y+z=
120
30
=4 units/day ----------(ii) and z+x=
120
24
=5 units/day ----------(iii) Adding equations (i), (ii) and (ii), we get : ⇒ 2(x+y+z)=6+4+5=15 ⇒ x+y+z=