Answer:
6.7% of children who finished the race in under 45 seconds.
Step-by-step explanation:
We are given the following information in the question:
Mean, μ = 75 seconds
Standard Deviation, σ = 20 seconds
We are given that the distribution of time of completion is a bell shaped distribution that is a normal distribution.
Formula:
[tex]z_{score} = \displaystyle\frac{x-\mu}{\sigma}[/tex]
P(finished the race in under 45 seconds.)
P(x < 45)
[tex]P( x < 45) = P( z < \displaystyle\frac{45 - 75}{20}) = P(z < -1.5)[/tex]
Calculation the value from standard normal z table, we have,
[tex]P(x < 45) = 0.067 = 6.7\%[/tex]
6.7% of children who finished the race in under 45 seconds.
