Ur answer would be B.. Hope it helps let me know if its right or not!
Answer:
0.969
Step-by-step explanation:
Given that:
Mean lifetime (m) = 520 hours
Variance = 900
Hence, standard deviation (s) = √900 = 30
Probability that bulb will last for at most 576 hours
X ≤ 576
Obtain the standardized score :
Using the relation :
Zscore = (x - m) / s
Zscore = (576 - 520) / 30
Zscore = 56 / 30
Zscore = 1.867
P(Z ≤ 1.867) : using the z probability calculator ;
P(Z ≤ 1.867) = 0.96905
Hence, P(Z ≤ 1.867) = 0.969
Answer:
5 seconds
Step-by-step explanation:
The relationship between "d" and "the ground" is not described. If we assume that "d" is distance above the ground, then the rock will hit the ground when d=0. This gives rise to the quadratic equation ...
-t^2 +4t +5 = 0
-(t -5)(t +1) = 0
t = 5 or t = -1 are solutions. Only the positive solution is useful.
The rock will hit the ground after 5 seconds.
A) 3.5
B) 9.8666
Hope this helps