From the book “Recreational Mathematics” by Malba Tahan
Doctor Túlio, professor of mathematics, to punish one of his students, a young vagrant and inattentive, gave him the following task:
Multiply decimals: 2.4142136 x 1.4142136
The student, who hated numerical calculations, noting that the decimal parts of the factors were equal, proceeded as follows, quite absurd and wrong:
Added the whole parts and kept the same decimal part. And, very lighthearted, he took his bill to the teacher and said:
“There, Professor Tulio. I already made yours exactly. It's one hundred percent cool. The result is 3.4142136.
And ran to the playground.
The Doctor. Túlio, who is a mathematician (he was a disciple of Prof. Lacaz Neto), thought it would be prudent to check. The boy had done the punishment too quickly. And the teacher, when performing the tremendous multiplication, discovered something really amazing: the student, with his original and absurd system of multiplication, had got it right! The product was exactly 3.4142136.
Mathematics, in fact, is a prodigious science.
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