Culegere Matematica | Clasa A 9 A !new!

“The equations force the son to be 9 and the father 36, with sum 45. Since 45 is composite (3 × 15, 5 × 9), the condition ‘sum is prime’ cannot be met. Therefore, no such ages exist in whole numbers.”

But the next problem stopped him cold. Problem 790: A different father is four times as old as his son. In 18 years, he will be only twice as old. But the sum of their current ages is a prime number. Find their ages. culegere matematica clasa a 9 a

Andrei stared at the page. For the first time, the culegere wasn’t asking for a number. It was asking for a reason . He wrote in his notebook: “The equations force the son to be 9

He checked twice. No mistake. He checked the answer key at the back—it only said “Impossible. Explain why.” Problem 790: A different father is four times