Need your students to improve or practice their calculator skills with decimals and rounding? Try this! All of my riddles (including this one) are designed with TI-15 Calculators in mind, but you can tweak it to work with any scientific calculator that has rounding decimal and whole number keys. I structure the document so that the students feel as though they are solving riddles instead of just completing a worksheet. You can have them work in pairs or independently, but by the end of the activity I can promise this will give you a better idea of what your students may need more help in while also giving you teachable moments to give timely feedback.