Jika ²log 3 =p dan ³log5=q,maka ³log20

3 log 20 = 3 log 4 + 3 log 5
= 3 log 2^2 + 3 log 5
= 2 (3 log 2) + 3 log 5
= 2(1 / 2 log 3) + 3 log 5
= 2 (1/p)+ q
= 2/p + q
= 2/p + pq / p
= 2 + pq / p