Answer:
Architect
Explanation:
Mechanic : will use fractions of the time, since his tools are labeled like 3 3/8 or 2 7/8, but not much decimals, except for his billing.
Dr : Rarely use decimals, except for reading lab reports (for blood analysis for example), prescriptions are in whole numbers, occasionally in fractions.
Lawyer : Never, his bills are in round numbers, and the only decimal points he would use would be to refer to law articles numbers.
Architect : All the time, for measurements on plans, to determine the quantity of materials needed, and so on.
Historian: Almost never... since he deals mostly with years and dates.