x years old in the year x squared
A 19th-century mathematician, who died in 1871, once said: “I was years old in the year .”
How old was he in that year?
Fractions, decimals with at least 3 significant digits, and expressions such as sqrt(2)/2, e^-1 or pi/4.
Which perfect squares are years in the 19th century?
, , .
h
s Shown after a correct answer. Revealing it first marks the problem as seen, not solved.
Idea. The year must be a perfect square during his lifetime, and squares near 1800 are far apart, so there is only one candidate.
Step 1. The squares near his lifetime are , and .
Step 2. 1936 is after his death. In 1764 he would have been 42, born in 1722, so he would have died at about 149: impossible. In 1849 he was 43, born in 1806, and died at 65.
So he was 43, in 1849. The mathematician is Augustus De Morgan.
A variant. Someone born in 1980 is 45 in .