Answer:
0.02275
Step-by-step explanation:
We have been given that the time needed to complete a final examination in a particular college course is normally distributed with a mean of 80 minutes and a standard deviation of 10 minutes. We are asked to find the probability of completing the exam in one hour or less.
We know that 1 hour equals 60 minutes. First of all, we will find the z-score corresponding to 60 minutes.

z = z-score,
x = Sample score,
= Mean,
= Standard deviation.



Now, we will use normal distribution table to find area under z-score of
as:


Therefore, the probability of completing the exam in one hour or less is 0.02275.
B) 4Na + O₂ → 2Na₂O
b) H₂ + Cl₂ ---> 2HCi
4 5/8 as an improper fraction is 37/8
——> 8*4=32 32+5=37
As a mixed number it is the same I think. 5 can’t decide into 8 so it stays 4 5/8.
Hopefully this helps...
A protractor can be used!