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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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