If you solve the rec reln by traditional method(by substitution and not by tree method)
you will see that T(n/(3/2)) will be like T(n/(3/2)^k) for k th transaction ....
so substitute T(1)=T(n/(3/2)^k) because we need to kind value of k such that we will reach the last stage of recurrence relation i.e. T(1)
thus we will get an idea of how deep the tree(it is quite intuitive !) will be (that's what the discussion was all about)
