on average, babies spend about twice as much time sleeping as adults. this means that there was a time when you slept as many as 18 hours a day! however, as a teenager or adult, you only require about eight or nine hours of sleep, and some people need as little as seven hours.능률 실용영어 1- 4과 본문인데요...
왜 똑같은 시간인데 (hours 라고 했는데) 위에는 many (가산명사)로 쓰고 아래는little(불가산 명사)로쓴건지이해가 어렵네요~~ 어떻게 구분해야 할지...

아시는 분 설명좀 부탁드릴게요^^