The mainsail of a sailboat is shaped like a right triangle with the dimensions shown. How much material was needed to make the s
ail?
a. 100 square feet
b. 544 square feet
c. 88 square feet
d. 272 square feet
a. 100 square feet
b. 544 square feet
c. 88 square feet
d. 272 square feet
2 answers:
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Answer:
0.0465 = 4.65% probability that at least 50 live in the northeast.
Step-by-step explanation:
I am going to use the normal approximation to the binomial to solve this question.
Binomial probability distribution
Probability of exactly x sucesses on n repeated trials, with p probability.
Can be approximated to a normal distribution, using the expected value and the standard deviation.
The expected value of the binomial distribution is:
The standard deviation of the binomial distribution is:
Normal probability distribution
Problems of normally distributed samples can be solved using the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
When we are approximating a binomial distribution to a normal one, we have that ,
.
In this problem, we have that:
So
Approximate the probability that at least 50 live in the northeast.
Using continuity correction, this is , which is 1 subtracted by the pvalue of Z when X = 49.5. So
has a pvalue of 0.9535
1 - 0.9535 = 0.0465
0.0465 = 4.65% probability that at least 50 live in the northeast.
Answer:
a. 18.5 degrees
b. 58.5 degrees
c. 24 hours
d. T(t) = 58.5 + 18.5cos(πt/12)
e. predicted: 53.7°, about 1.7° high
Step-by-step explanation:
No doubt your curriculum materials have examples of problems of this sort. You would do well to follow an example.
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There are several ways to go about making a sinusoidal model of this data, depending on the error you are willing to tolerate. The data can be modeled exactly using the result of a discrete Fourier Transform, but we suspect that is pretty far beyond the intended scope of the problem.
The easiest model to make is one that matches the extremes of the data, so that is what we'll describe here.
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a. The amplitude of the sinusoidal function can be computed as half the difference between the maximum (77) and minimum (40). So, the amplitude is ...
A = (77 -40)/2 = 37.2 = 18.5
The amplitude is 18.5 (degrees).
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b. The vertical shift can be computed as the average of the maximum and minimum:
D = (77 +40)/2 = 117/2 = 58.5
The vertical shift is 58.5 (degrees).
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c. The data is presumed to be periodic with a period of 24 hours.
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d. The temperature at t=0 is a maximum, so can be modeled best using a cosine function (which has a maximum when t=0). Using these parameters, the model is ...
T(t) = D + Acos(2π/period·t)
T(t) = 58.5 + 18.5cos(πt/12)
If you insist on a sine (not cosine) model, the sine function is the same as the cosine function when it is shifted left by 1/4 period.
T(t) = 58.5 +18.5sin(π(t+6)/12)
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e. 10 a.m. corresponds to 7 hours before t=0, so is t = -7 or +17.
T(17) = 58.5 +18.5cos(17π/12) ≈ 58.5 +18.5(-0.2588) ≈ 53.7
The predicted temperature at 10 a.m. is 53.7 °F. The actual value was 52 °F, so the prediction was a little high.
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The graph shows a plot of the given data points and the sinusoidal model we created. (It only matches the given data at the two extreme values used to create the model.)
