Answer: 15.86%
Step-by-step explanation:
Let x denotes the marks in Chemistry test.
Given : Marks on a Chemistry test follow a normal distribution with a mean of 72 and a standard deviation of 12.
i.e. [tex]\mu=72[/tex] and [tex]\sigma=12[/tex]
The probability that the students have scores below 60 :
[tex]P(x<60)=P(\dfrac{x-\mu}{\sigma}<\dfrac{60-72}{12})\\\\=P(z<-1)\ \ [\because\ z=\dfrac{x-\mu}{\sigma}]\\\\ =1-P(z<1)\ \ [\because\ P(Z<-z)=1-P(Z<z) ]\\\\=1-0.8414\ \ [\text{By z-table}]\\\\=0.1586=15.86\%[/tex]
Therefore , the approximate percentage of the students have scores below 60 = 15.86%
