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2 years ago

PLEASEEE SOMONEE HELP ASAP!!

Mathematics

1 answer:

Archy [21]2 years ago

6 0

Answer:

25 black keys

Step-by-step explanation:

Let the number of requires black keys = 'x'

White key : Black keys = 7 : 5

7 : 5 :: 35 : x

Product of extremes = product of means

7 *x = 35 * 5

x = $\frac{35*5}{7}$

x = 5 *5

x = 25

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A teacher is buying pencils for her classroom. If a dozen pencils cost $0.97, how many pencils can she purchase with $5?

mixas84 [53]

Answer:

The teacher can purchase 61 pencils with $5

Step-by-step explanation:

This is a simple proportion problem. It can be solved by pure logic reasoning without any formulas

It a dozen pencils cost $0.97, each pencil cost $0.97/12=0.08083

With $5 she will be able to purchase 5/0.08083=61.85 pencils

We must round to the nearest lower integer

The teacher can purchase 61 pencils with $5

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2 years ago

HELP A GIRL OUT

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The numbers are 9 and 27.

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2 years ago

"the life length x (in years) of a dvd player" is exponentially distributed with mean 5 years. what is the probability that a mo

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The exponential distribution is:
$\lambda e^{- \lambda x}$
where $\lambda = \frac{1}{mean}=\frac{1}{5}$

The probability we want is how likely will a dvd player last more than 8 years, given it has already lasted 5 years
To find this, you use conditional probability.
$P(A|B) = \frac{P(A and B)}{P(B)}$
where A is P(x>8) and B is P(x>5)
To find these probabilities, integrate over the distribution:
$P(x \ \textgreater \ N) = \int_N^{\infty} \frac{1}{5} e^{-x/5} dx = e^{-N/5}$

Sub into conditional probability formula:

$P(x \ \textgreater \ 8 | x\ \textgreater \ 5) = \frac{P(x\ \textgreater \ 8)}{P(x\ \textgreater \ 5)} = \frac{e^{-8/5}}{e^{-5/5}} = e^{-3/5} = 0.549$

Final Answer: Given a dvd player is more than 5 years old, the probability that it will last another 3 more years is about 54.9%

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2 years ago

Miranda earned $c for working 8 hours. Write an expression to show how much Miranda earned for each hour she worked.

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3 years ago

A treasure map says that a treasure is buried so that it partitions the distance between a rock and a tree in a 5:9 ratio. Marin

Tanya [424]

Let the coordinates of the treasure be (x,y).
Let $d_{1}$ = distance from the rock to the treasure.
Let $d_{2}$ = distance from the tree to the treasure.
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Note that 5/9 = 0.556 (approx)
Test (11.4, 14.2)
d1 = 14.8, d2 = 8.2, d1/d2 = 1.8 Incorrect
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Answer: The correct answer is (7.6, 8.8)

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2 years ago

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