Answer:
I got 219 but I'm not sure that's the answer.
Step-by-step explanation:
The distance is 19 yards or 18.9 yards:
because tan(10)=opposite/adjacent=3.33/x and x is distance
x=3.33/tan(10)=18.9 yd
The proportion is 0.4401.
We find z-scores that correspond with both ends of this interval. Z-scores are given using the formula:

For the lower end,

The proportion of scores to the left of this number is 0.2514.
For the higher end, the z-score is

The proportion of scores to the left of this number is 0.6915.
To find just the proportion of scores between these two, we subtract;
0.6915-0.2514 = 0.4401.
One fifth of the participants is 1/5*100=100/5=20 is the number of the participants given medicine. So the number of participants given placebo is 100-20=80.
80% of the 80 who took placebo felt improvements, so 20% of 80, which is
(20/100)*80=(2/10)*80=160/10=16 is the number of participants who took placebo and felt no improvement.
P(choosing participant who took placebo and felt no improvement)=
n(participant who took placebo and felt no improvement)/n(participants)
=16/100=0.16
I think the answer is 5, if you divide 7.5 by 1.45 you get 5.2 or 5.17 so approximately 5.