AP Statistics question that is vexing me

Question

Roseville Hospital emergency room normally admits six cardiac arrest patients in a day. What's the probability they admit more than two patients in an hour? In any thousand-hour period (about forty-two days), how many times would this happen, on average?

Answer 1

6 patients per day translates to a probability of 6/24 = 1/4 = 0.25 per event

for "more than two in an hour" =  0.25 x 0.25 x 0.25 = 0.0156 = 1/64

 

"how many times would this happen" (referring to "more than two an hour")

 

then, for 1000 hours (="opportunities"), 0.0156 x 1000 ≅ 15