Gallery Problems Exercise

A Number Trick

Work Time

A Number Trick

  1. Work with a partner. Give each of these directions to your partner, one at a time:
    • Write down a number, but don’t let me see which number you wrote.
    • Add 3 to your number.
    • Multiply that sum by 5.
    • Subtract 10 from that product.
    • Divide that difference by 5.
    • Subtract your original number from the quotient.
    • The difference is 1. Am I correct?
  2. Use what you know about simplifying expressions to show why the trick works.
  3. Make up your own number trick. Try it with your partner.