jika 2 log 3 = a dan 3 log 5 = b, maka 5 log 12/5 =

²log 3 = a
³log 5 = b

Sifat perkalian
²log 3 × ³log 5 = ²log 5 = ab.

Maka:
= ⁵log (12/5)
= ⁵log 12 - ⁵log 5
= ⁵log 2² + ⁵log 3 - ⁵log 5
= 2 × 1/(²log 5) + 1/(³log 5) - 1
= 2/a + 1/ab - 1