diketahui 2 log 3 = p dan 3 log 5 = q. 3 log 120 jika dinyatakan dengan p dan q adalah

3 log 5 = q
(log 5)/(log 3) = q
log 5 = q.log 3
log 3 = (log 5)/q

2 log 3 = p
(log3)/(log 2) = p
log 3 = p.log 2
log 2 = (log 3)/p

3 log 120 = (log 120)/(log 3)
              = (log 2^3.3.5)/(log 3)
              = {(3.log 3)/p + log 3 + q.log 3} / log 3
              = {log 3(3/p + 1 + q} / log 3
              = 3/p + q + 1