Video narration
During a classroom guessing game, can I predict your final answer without knowing your secret number? Choose any number in your head. Let's test four: double it to get eight, add ten to make eighteen, halve that to get nine, then subtract your starting number, four. Five. In the game, the result stays tied to your starting number at each step, so it can feel like I've guessed what you chose. But the trick isn't guessing your number. Doubling and then halving bring your original number back. The added ten is halved too, becoming five; subtract your original number, and only five remains. Call your secret number x: x becomes 2x, then 2x + 10, then x + 5, and finally 5. So, in our classroom guessing game, yes: whatever number you choose, doubling it, adding ten, halving it, then subtracting your number leaves five.