Let the general term of the expansion
Tr+1=60Cr(7)60−r(−3)′ =60Cr⋅(7)12−(−1)r⋅(3) Then, for getting rational terms,
r should be multiple of L.C.M. of (5,10)
Then,
r can be 0,10,20,30,40,50,60 .
Since, total number of terms
=61 Hence, total irrational terms
=61−7=54