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zubka84 [21]
3 years ago
13

John, Rick, and Molli can paint a room working together in 6 hours. Alone, John can paint the room in 12 hours. If Rick works al

one, he can paint the room in 15 hours. Write an equation comparing the group rate to the sum of the individual rates. Then find how long it will take Molli to paint the room if working alone.
Mathematics
1 answer:
Tresset [83]3 years ago
4 0

Answer:

\dfrac{1}{12}+\dfrac{1}{15}+\dfrac{1}{x}=\dfrac{1}{6}

60 hours

Step-by-step explanation:

John - 12 hours

Rick - 15 hours

Molli - x hours

Together - 6 hours

Each of them can paint:

John - \frac{1}{12} of a room per hour

Rick - \frac{1}{15} of a room per hour

Molli - \frac{1}{x} of a room per hour

Together - \frac{1}{6} of a room per hour

So the equation is

\dfrac{1}{12}+\dfrac{1}{15}+\dfrac{1}{x}=\dfrac{1}{6}

Solve this equation:

\dfrac{1}{x}=\dfrac{1}{6}-\dfrac{1}{12}-\dfrac{1}{15}\\ \\\dfrac{1}{x}=\dfrac{10-5-4}{60}=\dfrac{1}{60}\\ \\x=60

Molli can paint the room in 60 hours.

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Hi does anyone know how to solve this question if so please show the working out.
tester [92]

Explanation:

The Law of Sines is your friend, as is the Pythagorean theorem.

Label the unmarked slanted segments "a" and "b" with "b" being the hypotenuse of the right triangle, and "a" being the common segment between the 45° and 60° angles.

Then we have from the Pythagorean theorem ...

  b² = 4² +(2√2)² = 24

  b = √24

From the Law of Sines, we know that ...

  b/sin(60°) = a/sin(θ)

  y/sin(45°) = a/sin(φ)

Solving the first of these equations for "a" and the second for "y", we get ...

  a = b·sin(θ)/sin(60°)

and ...

  y = a·sin(45°)/sin(φ)

Substituting for "a" into the second equation, we get ...

  y = b·sin(θ)/sin(60°)·sin(45°)/sin(φ) = (b·sin(45°)/sin(60°))·sin(θ)/sin(φ)

So, we need to find the value of the coefficient ...

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Answer:

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Step-by-step explanation:

The first step is to find out how many times the wheels turn in one foot. The ratio of rotations per minute is 20:140. This can be simplified to 1:7, meaning there is 1/7 of a rotation for every 1 foot.

Next, we need to find out how many times they turn in one mile. The ratio is 1:7, and the 1 needs to become 5280. To do this, multiply both sides of the ratio by 5280. You will get 5280:36960, meaning there is 36960 rotations every mile (the ratio of miles to rotations is 1:36960).

Now, multiply 1:36960 by 5 to get the amount of rotations per every 5 miles. You will get 184800.

Final answer: the wheels turn 184800 times in 5 miles.

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