It is: MMMCVIII = 3108

12*7*37 = 3108

instructions for cardinal 3108 digital watch

31.08 x 2.35 = 73.038

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Comparing 3108 and 31.08 you find that 31.08 = 3108 ÷ 100

Comparing 235 and 2.35 you find that 2.35 = 235 ÷ 100

→ 31.08 × 2.35 = (3108 ÷ 100) × (235 ÷ 100)

= (3108 × 235) ÷ (100 × 100)

= (3108 × 235) ÷ 10000

we are told 3108 × 235, so can continue without having to do any (hard) calculation:

= 730380 ÷ 10000

= 73.038

They are member of the infinite set of numbers of the form 3108*k where k is an integer.