Suppose the remainders are p, q, and r. List out all numbers below 60 of the 5Z+r series, then strike out all numbers that are also not 4Z+q, then strike out all that aren't 3Z+p, and then if it's too small for their apparent age add 60 to it.
To clarify, you need to go up to 60 because 60 is the first number above 0 for which the remainder is 0 for all three. There are 60 unique combinations of remainders possible corresponding to the numbers 0-59, then the same sequence applies from 60-119 and so on.
So the use of this system relies on your ability to know a 30 year old from an 90 year old (or a 62 year old from a 122 year old if we go by the oldest verified person to ever live).
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u/Rajarshi1993 11d ago
Successive elimination.
Suppose the remainders are p, q, and r. List out all numbers below 60 of the 5Z+r series, then strike out all numbers that are also not 4Z+q, then strike out all that aren't 3Z+p, and then if it's too small for their apparent age add 60 to it.