Answer:
Step-by-step explanation:
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2 answers:
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Answer:
(a) 0.6579
(b) 0.2961
(c) 0.3108
(d) 240
Step-by-step explanation:
The random variable <em>X</em> can be defined as the number of particles in a suspension.
The concentration of particles in a suspension is 50 per ml.
Then in 5 mL volume of the suspension the number of particles will be,
5 × 50 = 250.
The random variable <em>X</em> thus follows a Poisson distribution with parameter, <em>λ</em> = 250.
The Poisson distribution with parameter λ, can be approximated by the Normal distribution, when λ is large say λ > 10.
The mean of the approximated distribution of X is:
μ = λ = 250
The standard deviation of the approximated distribution of X is:
σ = √λ = √250 = 15.8114
Thus,
(a)
Compute the probability that the number of particles withdrawn will be between 235 and 265 as follows:
Thus, the value of P (235 < <em>X</em> < 265) = 0.6579.
(b)
Compute the probability that the average number of particles per mL in the withdrawn sample is between 48 and 52 as follows:
Thus, the value of .
(c)
A 10 mL sample is withdrawn.
Compute the probability that the average number of particles per mL in the withdrawn sample is between 48 and 52 as follows:
Thus, the value of .
(d)
Let the sample size be <em>n</em>.
The value of <em>z</em> for this probability is,
<em>z</em> = 1.96
Compute the value of <em>n</em> as follows:
Thus, the sample selected must be of size 240.
Answer:
Length of the ladder used by worker = 17 feet
Step-by-step explanation:
Given:
Height of the window from the ground = 13 ft
Distance of fence from the building = 3 ft
Distance of ladder from the building = (3+8) = 11 ft
We have to find the length of the ladder.
Let the length of the ladder be 'x'
From the diagram we can also say that 'x' is the hypotenuse of the right angled triangle.
Using Pythagoras formula:
⇒
Here base length = 11 ft
Perpendicular = 13 ft
Plugging the values:
⇒
⇒
⇒
⇒ feet
The length of the ladder = 17 feet to its nearest tenth.
