Lizzy: While preparing balloons for Eva's birthday party, her mom bought 50 balloons and 1800cm³ of helium. One balloon needs 50cm³ to float high enough to touch the ceiling, and she can fill any remaining balloon with ordinary air. If she used up all of the helium and inflated every balloon, how many more balloons are touching the ceiling than not?.
Me: Hmmm, let me think. I think this is the detailed solution:
50cm³ will make one balloon touch the ceiling so 1800cm³ will make 1800 / 50 = 36 balloons touch the ceiling. There are 50 balloons in total so 50 - 36 = 14 balloons will not float since they were filled with ordinary air. There are 36 - 14 = 22 more balloons touching the ceiling than not. Final answer: 22.