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4 years ago

25% of all who enters a race do not complete. 30 haveentered.

Mathematics

1 answer:

nikklg [1K]3 years ago

6 0

Answer:

The probability that exactly 5 are unable to complete the race is 0.1047

Step-by-step explanation:

We are given that 25% of all who enters a race do not complete.

30 have entered.

what is the probability that exactly 5 are unable to complete the race?

So, We will use binomial

Formula : $P(X=r) =^nC_r p^r q^{n-r}$

p is the probability of success i.e. 25% = 0.25

q is the probability of failure = 1- p = 1-0.25 = 0.75

We are supposed to find the probability that exactly 5 are unable to complete the race

n = 30

r = 5

$P(X=5) =^{30}C_5 (0.25)^5 (0.75)^{30-5}$

$P(X=5) =\frac{30!}{5!(30-5)!} \times(0.25)^5 (0.75)^{30-5}$

$P(X=5) =0.1047$

Hence the probability that exactly 5 are unable to complete the race is 0.1047

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Help!

MAXImum [283]

Answer:

1) The equation for the of the ball in y = a·(x - h)² + k is;

y = -16·(x - 5)² + 25

2) The height of the dock, d = -375 feet below the water level

Step-by-step explanation:

1) The question is with regards to quadratic function representing projectile motion

The given parameters are;

The height the ball reaches 4 seconds after Sarah kicked the ball = 9 feet

The time the ball hits the water = 6 seconds after reaching the 9 feet height

The form of the quadratic equation representing the motion is given as follows;

y = a·(x - h)² + k = a·x² - 2·a·h·x + a·h² + k

Let 'x' represent the time of motion of the ball, and let 'a', represent the acceleration due to gravity, we have;

The equation for the ball, y = a·(x - h)² + k

Where;

(h, k) = The coordinates of the vertex

h = The horizontal component of the vertex coordinate = 0

Therefore, we have;

When x = 0, y = d

d = -16·(0 - h)² + k = -16·h² + k

d = -16·h² + k

When x = 4, y = 9 - d

9 - d = -16(4 - h)² + k = -16(4 - h)² + k

When x = 2, y = d

d = -16(2 - h)² + k

When x = 6, y = 9

9 = -16(6 - 5)² + k

When x = 8, y = d

d = -16(8 - h)² + k

-16(8 - h)² - (-16(2 - h)²) = 0

h = 5

From 9 - d = -16(4 - h)² + k = -16(4 - 4)² + k

d = 9 - k

9 = -16(6 - h)² + k

k = 9 + 16(6 - 5)² = 25

d = 9 - k = 9 - 25 = -16

Therefore, h = 5, k = 25

The equation for the of the ball in y = a·(x - h)² + k is therefore;

y = -16·(x - 5)² + 25

2) When x = 0, y = d, ∴ d = -16(0 - 5)² + 25 = -375 feet below the water

The height of the dock, d = -375 feet below the water level

6 0

3 years ago

A rectangular pool is 20 feet wide and 50 feet long. A deck used for sunning surrounds the pool. The deck is the same width all

rodikova [14]

Answer:

3 feet

Step-by-step explanation:

Let x represent the width of the deck. The deck adds to the pool dimensions on both sides, so the area of the site including pool and deck will be ...

A = (20 +2x)(50 +2x) = 1000 +140x +4x^2

The area of the pool alone is

A = (20)(50) = 1000

So, the area of the deck is the difference:

456 = (4x^2 +140x +1000) -(1000)

Dividing by 4 and subtracting 114, we have ...

x^2 +35x -114 = 0

(x -3)(x +38) = 0

Solutions to this are x = 3 and x = -38. The positive solution is the one of interest.

The deck is 3 feet wide.

4 0

3 years ago

Simplify when it is possible 10 x^2 - y + x^2

Romashka-Z-Leto [24]

Combine like terms
11x^2 - y

5 0

3 years ago

As shown in the illustration, Alexa had a negative balance in her checking account before depositing a $47.00 check. What is the

meriva

Well, I can't really answer the question without seeing the illustration, I cannot tell you what Alex's checking account balance is now, because of the fact that I do not know what it was before. If you change the question so it includes this, I would be delighted to help you!

3 0

4 years ago

(1 point) A recent report for a regional airline reported that the mean number of hours of flying time for its pilots is 56 hour

Ray Of Light [21]

Answer:

(53.812 ; 58.188) ; 156

Step-by-step explanation:

Given that :

Sample size (n) = 51

Mean (m) = 56

Standard deviation (σ) = 9.5

α = 90%

Using the relation :

Confidence interval = mean ± Error

Error = Zcritical * (standard deviation / sqrt (n))

Zcritical at 90% = 1.645

Error = 1.645 * (9.5 / sqrt(51))

Error = 1.645 * 1.3302660

Error = 2.1882877

Hence,

Confidence interval :

Lower boundary = 56 - 2.1882877 = 53.8117123

Upper boundary = 56 + 2.1882877 = 58.1882877

Confidence interval = (53.812 ; 58.188)

2.)

Margin of Error (ME) = 1.25

α = 90%

Sample size = ((Zcritical * σ) / ME)^2

Zcritical at 90% = 1.645

Sample size = ((1.645 * 9.5) / 1.25)^2

Sample size = (15.6275 / 1.25)^2

Sample size = 12.502^2 = 156.3000

Sample size = 156

3 0

3 years ago