Answer: 0.0228
Step-by-step explanation:
Given : The mean and the standard deviation of finish times (in minutes) for this event are respectively as :-

If the distribution of finish times is approximately bell-shaped and symmetric, then it must be normally distributed.
Let X be the random variable that represents the finish times for this event.
z score : 

Now, the probability of runners who finish in under 19 minutes by using standard normal distribution table :-

Hence, the approximate proportion of runners who finish in under 19 minutes = 0.0228
AB = ==> distance between the bottom of the plank; and the wall ===> 3 ft.
C ====> 49 degrees
For letter a, to solve for AC:
AC ==> HYPOTENUSE. The angle C is the OPPOSITE side of AB.
use sine :
sin A ===> opposite/hypotenuse
Solve:
sin 49 ====> 3/AC
AC ====> 3 / sin 49
AC ====> 3.96 ft.
For letter b, to solve for BC:
We are now given with the base (3 ft.); and; the hypotenuse (3.96 ft.) so we can use the Pythagorean theorem:
a^2 + b^2 = c^2
Let:
a ===> AB
b ===> BC
c ===> AC
(AB)^2 + (BC)^2 ===> (AC)^2
3^2 + (BC)^2 ===> (3.96)^2
(BC)^2 ===> (3.96)^2 - 3^2
(BC)^2 ===> 6.6816
sqrt (BC)^2 ===> sqrt 6.6816
Answer: BC ===> 2.58 ft.
Hope that helps!!!! : )
I dont know i will tell you when i find out