1. Jean looked at the boy’s sheet of paper. “Another of your crazy multiplications,” she said. “Of course I can’t do it in my head, but what’s the trick?” “An easy one,” Adam replied. “To multiply that by eighteen, you just increase each figure by one and then write a four in front. It’s the smallest number that works exactly that way.” Simple! But what was Adam’s number?

Adam’s number was 49822

Adam’s number was 83421

Adam’s number was 24183