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tatuchka [14]
2 years ago
9

2. Carl needs 15 hours longer than Jennifer to paint a room. If they work together, they can complete the job in 4 hours. Explai

n each step in figuring out how to determine the time it would
take Jennifer to complete this job on her own. Pls help 20 minutes left
Mathematics
1 answer:
nasty-shy [4]2 years ago
4 0

Answer:

Jennifer would complete the job on her own in 5 hours.

Step-by-step explanation:

Solving a quadratic equation:

Given a second order polynomial expressed by the following equation:

ax^{2} + bx + c, a\neq0.

This polynomial has roots x_{1}, x_{2} such that ax^{2} + bx + c = a(x - x_{1})*(x - x_{2}), given by the following formulas:

x_{1} = \frac{-b + \sqrt{\Delta}}{2*a}

x_{2} = \frac{-b - \sqrt{\Delta}}{2*a}

\Delta = b^{2} - 4ac

Rates

The together rate is the sum of their separates rate.

We have that:

Jennifer takes x hours to complete the job on her own, so her rate is 1/x.

Carl needs 15 hours longer than Jennifer, that is, 15 + x hours, so his rate is 1/(15+x).

The together rate is 1/4. So

\frac{1}{4} = \frac{1}{x} + \frac{1}{15+x}

\frac{1}{4} = \frac{15 + x + x}{x(15+x)}

\frac{1}{4} = \frac{15 + 2x}{x(15+x)}

Applying cross multiplication.

x^2 + 15x = 4(15 + 2x)

x^2 + 15x = 60 + 8x

x^2 + 7x - 60 = 0

Quadratic equation with a = 1, b = 7, c = -60. So

\Delta = 7^{2} - 4*1*60 = 289

x_{1} = \frac{-7 + \sqrt{289}}{2} = 5

x_{2} = \frac{-7 - \sqrt{289}}{2} = -12

Since the time to complete the job has to be a positive value.

Jennifer would complete the job on her own in 5 hours.

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Answer:

The minimum head breadth that will fit the clientele is 4.4 inches.

The maximum head breadth that will fit the clientele is 7.8 inches.

Step-by-step explanation:

Let <em>X</em> = head breadths of men that is considered for the helmets.

The random variable <em>X</em> is normally distributed with mean, <em>μ</em> = 6.1 and standard deviation, <em>σ</em> = 1.

To compute the probability of a normal distribution we first need to convert the raw scores to <em>z</em>-scores using the formula:

z=\frac{x-\mu}{\sigma}

It is provided that the helmets will be designed to fit all men except those with head breadths that are in the smallest 4.3% or largest 4.3%.

Compute the minimum head breadth that will fit the clientele as follows:

P (X < x) = 0.043

⇒ P (Z < z) = 0.043

The value of <em>z</em> for this probability is:

<em>z</em> = -1.717

*Use a <em>z</em>-table.

Compute the value of <em>x</em> as follows:

z=\frac{x-\mu}{\sigma}\\-1.717=\frac{x-6.1}{1}\\x=6.1-(1.717\times 1)\\x=4.383\\x\approx4.4

Thus, the minimum head breadth that will fit the clientele is 4.4 inches.

Compute the maximum head breadth that will fit the clientele as follows:

P (X > x) = 0.043

⇒ P (Z > z) = 0.043

⇒ P (Z < z) = 1 - 0.043

⇒ P (Z < z) = 0.957

The value of <em>z</em> for this probability is:

<em>z</em> = 1.717

*Use a <em>z</em>-table.

Compute the value of <em>x</em> as follows:

z=\frac{x-\mu}{\sigma}\\1.717=\frac{x-6.1}{1}\\x=6.1+(1.717\times 1)\\x=7.817\\x\approx7.8

Thus, the maximum head breadth that will fit the clientele is 7.8 inches.

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Answer:

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Step-by-step explanation:

We are given that Seven-ninths (7/9) of the pencils in a box are yellow and three-tenths (3/10) of the yellow pencils are sharpened.

To find the fraction that represents sharpened yellow pencils, we find the product of the the fraction of yellow pencils and the fraction of yellow pencils that are sharpened.

That is:

=> (7 / 9) * (3 / 10)

=(7 * 3) / (9 * 10)

= 21 / 90

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