Heeeeeelllp please. 15 points

Terri Vogel, an amateur motorcycle racer, averages 129.71 seconds per 2.5 mile lap (in a 7 lap race) with a standard deviation o

Vikki [24]

Answer:

(a) The percent of her laps that are completed in less than 130 seconds is 55%.

(b) The fastest 3% of her laps are under 125.42 seconds.

(c) The middle 80% of her laps are from 126.80 seconds to 132.63 seconds.

Step-by-step explanation:

The random variable X is defined as the number of seconds for a randomly selected lap.

The random variable X is normally distributed with mean, μ = 129.71 seconds and standard deviation, σ = 2.28 seconds.

Thus, $X\sim N(129.71,\ 2.28^{2})$ .

(a)

Compute the probability that a lap is completes in less than 130 seconds as follows:

$P(X$

$=P(Z$

The percentage is, 0.55 × 100 = 55%.

Thus, the percent of her laps that are completed in less than 130 seconds is 55%.

(b)

Let x represents the 3rd percentile.

That is, P (X < x) = 0.03.

⇒ P (Z < z) = 0.03

The value of z for the above probability is:

z = -1.88

Compute the value of x as follows:

$z=\frac{x-\mu}{\sigma}\\-1.88=\frac{x-129.71}{2.28}\\x=129.71-(1.88\times 2.28)\\x=125.4236\\x\approx 125.42$

Thus, the fastest 3% of her laps are under 125.42 seconds.

(c)

Let x₁ and x₂ be the values between which the middle 80% of the distribution lie.

That is,

$P(x_{1}$

The value of z for the above probability is:

z = 1.28

Compute the values of x₁ and x₂ as follows:

$-z=\frac{x_{1}-\mu}{\sigma}\\-1.28=\frac{x_{1}-129.71}{2.28}\\x_{1}=129.71-(1.28\times 2.28)\\x=126.7916\\x\approx 126.80$ $z=\frac{x_{2}-\mu}{\sigma}\\1.28=\frac{x_{2}-129.71}{2.28}\\x_{2}=129.71+(1.28\times 2.28)\\x=132.6284\\x\approx 132.63$

Thus, the middle 80% of her laps are from 126.80 seconds to 132.63 seconds.

5 0

4 years ago

Is 1/2 equivalent to 5/8

kompoz [17]

No.

To check this yourself, you need the denominators to be the same to be able to easily compare the two.

For example, does 5/8 = 40/64?

1. Determine what you would need to do to the denominator in 5/8 to make it 64. (Multiply it by 8)
2. Find what fraction is equal to 1 with a denominator of 8. (8/8)
3. Multiply the fraction 5/8 by the one you just found (8/8), numerator times numerator, denominator times denominator.
4. Compare the answer with the second fraction.

It is important that when you multiply the denominator by any number you multiply the numerator by the same number. This is to preserve the fraction's value. This works because any number divided by itself is equal to 1, AND when you multiply any number by 1 (whether 1 is in the form of 1 or 4/4 or 8/8 or 234/234), the answer is always equal to the original number.

Another way to check would be to simply enter 1/2 into a calculator, write down the answer. Next enter 5/8 into a calculator. If the answers are the same, they are equal.

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