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Galina-37 [17]
3 years ago
5

The completion time for an exam is normally distributed with expected value 75 minutes and variance 12 minutes. What is the prob

ability that a student will finish this exam in less than 70 minutes or more than 80 minutes?
Mathematics
1 answer:
Debora [2.8K]3 years ago
5 0

Answer:

14.89% or 0.1489

Step-by-step explanation:

First, find the z-score for both 70 and 80 minutes and their corresponding percentile.

z= \frac{X - \mu }{SD} \\SD=\sqrt{V} =\sqrt{12}\\\mu =75\\z= \frac{X - 75}{\sqrt{12}}\\\\

For X = 70 minutes:

z= \frac{70 - 75}{\sqrt{12}}\\z=-1.4434

This z-score is equivalent to the 7.445 th percentile, so the probability of a student finishing this exam in less than 70 minutes is 7.445%

or X = 80 minutes:

z= \frac{80 - 75}{\sqrt{12}}\\z=1.4434

This z-score is equivalent to the 92.555 th percentile, so the probability of a student finishing this exam in more than 80 minutes is 100- 92.555 = 7.445%

Therefore, the probability (P) of a student finishing this exam in less than 70 minutes or more than 80 minutes is:

P = 7.445% + 7.445% = 14.89%

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skew-symmetric 3 x 3 matrices form as subspace of all 3 x 3 matrices and find a basis for this subspace.
Neporo4naja [7]

Answer:

a) ∝A ∈ W

so by subspace, W is subspace of 3 × 3 matrix

b) therefore Basis of W is

={ {\left[\begin{array}{ccc}0&1&0\\-1&0&0\\0&0&0\end{array}\right] ,\left[\begin{array}{ccc}0&0&1\\0&0&0\\-1&0&0\end{array}\right] ,\left[\begin{array}{ccc}0&0&0\\0&0&1\\0&-1&0\end{array}\right]}

Step-by-step explanation:

Given the data in the question;

W = { A| Air Skew symmetric matrix}

= {A | A = -A^T }

A ; O⁻ = -O⁻^T        O⁻ : Zero mstrix

O⁻ ∈ W

now let A, B ∈ W

A = -A^T       B = -B^T

(A+B)^T = A^T + B^T

= -A - B

- ( A + B )

⇒ A + B = -( A + B)^T

∴ A + B ∈ W.

∝ ∈ | R

(∝.A)^T = ∝A^T

= ∝( -A)

= -( ∝A)

(∝A) = -( ∝A)^T

∴ ∝A ∈ W

so by subspace, W is subspace of 3 × 3 matrix

A ∈ W

A = -AT

A = \left[\begin{array}{ccc}o&a&b\\-a&o&c\\-b&-c&0\end{array}\right]

= a\left[\begin{array}{ccc}0&1&0\\-1&0&0\\0&0&0\end{array}\right] +b\left[\begin{array}{ccc}0&0&1\\0&0&0\\-1&0&0\end{array}\right] +c\left[\begin{array}{ccc}0&0&0\\0&0&1\\0&-1&0\end{array}\right]

therefore Basis of W is

={ {\left[\begin{array}{ccc}0&1&0\\-1&0&0\\0&0&0\end{array}\right] ,\left[\begin{array}{ccc}0&0&1\\0&0&0\\-1&0&0\end{array}\right] ,\left[\begin{array}{ccc}0&0&0\\0&0&1\\0&-1&0\end{array}\right]}

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Step-by-step explanation:

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