Among the natural numbers below 100, there are 30 with a special property. Jovan has listed them in the table here.
But Jovan made a mistake, and one of these numbers must be replaced. Which number must be inserted in place of the incorrect number?
The number 75 must be replaced by the number 74. The numbers in the table are each the product of two prime numbers, ordered by size. The 75 does not fit with the other numbers because it is the product of three prime numbers.
We’d love to hear from you! E-mail us at games@sciam.com to share your experience.
This puzzle originally appeared in Spektrum der Wissenschaft and was reproduced with permission.
