Answer to B) is 7 months. Don’t quite understand A) though. More information about how many months you have to show for, would be quite helpful:)
The probability of the door opening within three attempts is the answer. C
The answer is 5/4 or 1 and 1/4 (both answers are correct just different forms), hope this helps !
A=2<span>πr(r+h)
</span>80π=<span>2π(5)(5+h)
</span>80π=10π(5+h)
80π=50π + 10πh
30π=10πh
3=h
