#72 A long lane
The mathematician Professor Numero lives at number 13 Long Lane, the same road as his good friend Professor Lemma, who is at number 156. The friends like that their house numbers when multiplied together are exactly divisible by the two numbers added together. However, Numero has always had his eye on number 28, which he thinks is “perfect”. “If only Lemma could also move so that our houses still had the same mathematical relationship,” says Numero. Bearing in mind that Long Lane lives up to its name, what is the biggest house number that Lemma could…
