Water Balloon Mishap!

Another 3-Act Math Problem.

I originally created this problem for the iBook I made for Linear Relations. I used the problem with grade 9 academics on the first day of school this year to get them introduced to the 3-Act style of questions.

This problem also has worked well with a grade 9 applied class when working with ratios and rates.

Here’s the problem,


Ask students: What were your “Wonder Questions” – What did you wonder?

Students will most likely ask when will the balloon explode, or how much water is in the balloon.

Ask Students: What information would you need to know?



Teacher Note: When I did this problem with students I was interested in applying rates, so when students wanted to know how big the balloon would get I told them the standard balloon will hold 14 Litres of water. If I was doing this near the end of the course I would tie in the volume of a sphere [Most balloons will have about 12 inch diameter.]



iPhone Charger

Act 1- Video

When will the phone charge?
1. Give an answer that is too high.
2. Give an answer that is too low.
3. Find how long it will take to charge.

Act 2 – hints
1. Make a table of values comparing the time and the percentage.
2. Graph the relation.
3. Find an equation to model this relation.

Act 3 – Video

1. What could cause the difference in answers?