by Dan Meyer

• 1. What will be the percent tint with both sunglasses?
• 2. Write a guess.
• 3. Write a guess you know is too high.
• 4. Write a guess you know is too low.

• video — double sunglasses

• video — the answer

• 5. Can you reach 100% tint this way? How many 50% tint sunglasses would you have to wear?.
• 6. How many 5% tint sunglasses would you have to wear to reach 60% tint?.

• video — 60% tint