A YouTube video is 100 hours long. Lila decides to watch it at two times the average speed. Roger, her friend, also watch the same video at the average speed. If they both watched six of the same videos, what's the total number of hours they watched?
Thoughts? Step-by-step reasoning:
When Lila watches the video at twice the normal speed, the video takes 100 / 2 = 50 hours. When she watches six such videos, the total number of video hours becomes 50 * 6 = 300 hours. Roger, her friend, watches 6 videos at the normal speed, which is 6 * 100 = 600 video hours. The total number of hours watched by the two is 600 + 300 = 900 hours.
Thus, the answer is 900.