The first flight out of Phoenix airport had a late departure. If the next three flights departed on-time, how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be higher than 70%?
Select the correct option:
A) 6	B) 5	C) 8	D) 9	E) 10
We need on-time departure rate to be higher than 7/10, so it should be at least 8/11, which means that 8 out of 11 flights must depart on time. Since for now 3 out of 4 flights departed on time then  8-3= 
<gadget id="calculator"> 8-3</gadget>
<output>5</output>
5 subsequent flights need to depart on-time.   Answer: 5
<result>B</result>
The first flight out of Phoenix airport had a late departure. If the next three flights departed on-time, how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be higher than 70%?