Brihat Parashara Hora Shastra
उभयत्र गते खेटे कार्यं त्रिगुणमेव हि । हानिद्वयेऽर्धहानिः स्यादित्यायुः प्रस्फुटं नृणाम् ॥ २२॥
If doubling and trebling is warranted, only trebling be done. In case of reductions also only halving is to be done, if both halving and reducing a third are required. That is how the final life-span of men be understood.
english translation
ubhayatra gate kheTe kAryaM triguNameva hi । hAnidvaye'rdhahAniH syAdityAyuH prasphuTaM nRNAm ॥ 22॥
hk transliteration by Sanscript