Answer:
The correct option is D. 81.8%
Step-by-step explanation:
Mean of the data set is given to be 40
⇒ μ = 40
Standard deviation of the data set is given to be 5
⇒ σ = 5
Now we are supposed to find out what percent of the numbers fall between 35 and 50
Now for P(35 < x < 50) :
Substitute x = 35 ⇒ z = -1
Substitute x = 50 ⇒ z = 2
So, P(-1 < z < 2) = P(z < 2) - P(z < -1)
⇒ P(-1 < z < 2) = 0.9772 - 0.1587
⇒ P(-1 < z < 2) = 0.8185
⇒ P(-1 < z < 2) = 81.8%
Therefore, 81.8% percent of the numbers fall between 35 and 50
Hence, The correct option is D. 81.8%