Changing Unit Speed
Sum of Consecutive Integers
Alternative Graphical Solution
@azhong392 Thanks for noticing this! This is a typo. The answer is correct, but the multiplication should say \(12 \times 6 = 72.\) It's been fixed now. Thanks very much for letting us know!
Continuous Changing Speed, Acceleration
@userusername Thanks so much for letting us know! I've fixed this now.