快猫短视频

#63 A 2025 puzzle

Set by Katie Steckles

The number 2025 can be split into two two-digit numbers: 20 and 25. If we add these together (20 + 25 = 45) and square the result, we get 45² = 2025.

By changing one digit of the number 2025, can you find another number that shares this property?

There is only one other four-digit number that returns itself when split in half, summed and squared. It ends in a 1. What might the last digit of its square root be?

All four of this number鈥檚 digits are different. What is it?

Solution next week

#62 Particular patterns in piles

Solution

There are three ways to arrange five balls, five ways to arrange six balls and 22 ways to arrange nine balls. (This might start off looking like the Fibonacci sequence, but it fails after eight balls!)