Fraction of black pens = 2/ (2 + 5) = 2/7 answer
Answer:
Step-by-step explanation:
Let x be the random variable representing the times a fire department takes to arrive at the scene of an emergency. Since the population mean and population standard deviation are known, we would apply the formula,
z = (x - µ)/σ
Where
x = sample mean
µ = population mean
σ = standard deviation
From the information given,
µ = 6 minutes
σ = 1 minute
the probability that fire department arrives at the scene in case of an emergency between 4 minutes and 8 minutes is expressed as
P(4 ≤ x ≤ 8)
For x = 4,
z = (4 - 6)/1 = - 2
Looking at the normal distribution table, the probability corresponding to the z score is 0.023
For x = 8
z = (8 - 6)/1 = 2
Looking at the normal distribution table, the probability corresponding to the z score is 0.98
Therefore,
P(4 ≤ x ≤ 8) = 0.98 - 0.23 = 0.75
The percent of emergencies that the fire department arrive at the scene in between 4 minutes and 8 minutes is
0.75 × 100 = 75%
Let 4 + 3x = u
then 3dx = du
or, <span>1/3∫<span>u√</span>du
</span>
= <span>1/3<span>u^<span>3/2</span></span>/(3/2)
</span>
= <span>2/9∗(4+3x<span>)^<span>3/2
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