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fenix001 [56]
3 years ago
7

A closet contains n pairs of shoes. If 2r shoes are chosen at random, (where 2r < n), what is the probability that there will

be
a) no complete pair
b) Exactly one complete pair
c) Exactly 2 complete pair
Mathematics
1 answer:
Pie3 years ago
4 0
We are choosing 2
2
r
shoes. How many ways are there to avoid a pair? The pairs represented in our sample can be chosen in (2)
(
n
2
r
)
ways. From each chosen pair, we can choose the left shoe or the right shoe. There are 22
2
2
r
ways to do this. So of the (22)
(
2
n
2
r
)
equally likely ways to choose 2
2
r
shoes, (2)22
(
n
2
r
)
2
2
r
are "favourable."

Another way: A perhaps more natural way to attack the problem is to imagine choosing the shoes one at a time. The probability that the second shoe chosen does not match the first is 2−22−1
2
n
−
2
2
n
−
1
. Given that this has happened, the probability the next shoe does not match either of the first two is 2−42−2
2
n
−
4
2
n
−
2
. Given that there is no match so far, the probability the next shoe does not match any of the first three is 2−62−3
2
n
−
6
2
n
−
3
. Continue. We get a product, which looks a little nicer if we start it with the term 22
2
n
2
n
. So an answer is
22⋅2−22−1⋅2−42−2⋅2−62−3⋯2−4+22−2+1.
2
n
2
n
⋅
2
n
−
2
2
n
−
1
⋅
2
n
−
4
2
n
−
2
⋅
2
n
−
6
2
n
−
3
⋯
2
n
−
4
r
+
2
2
n
−
2
r
+
1
.
This can be expressed more compactly in various ways.
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Vera_Pavlovna [14]
<h2>Hello!</h2>

The answer is:

The x-coordinate of the solution to the system of equations is:

x=-2

<h2>Why?</h2>

We can solve the problem writing both equations as a system of equations.

So, we are given the equations:

\left \{ {{y=x+4} \atop {3y=-2x+2}} \right.

Then, solving by reduction we have:

Multiplying the first equation by 2 in order to reduce the variable "x", we have:

\left \{ {{2y=2x+2*4} \atop {3y=-2x+2}} \right.

5y=2x-2x+8+2\\\\5y=8+2\\\\y=\frac{10}{5}=2

Now, substituting "y" into the first equation, to isolate "x" we have:

y=x+4\\\\2=x+4\\\\x=2-4=-2

Hence we have that the x-coordinate of the solution to the system of equations is

x=-2

Have a nice day!

3 0
3 years ago
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icang [17]

Answer:

4.5 feet = 1.5 yards

Step-by-step explanation:

1 yard equals 3 feet

Then:

1 ----- 3

x -----4.5

x = 4.5/3 = 1.5 yards

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3 years ago
Hannah and Dawson have both invested money in savings accounts with APYs of 3.2%. If Hannah's account has a balance of $31,000 a
9966 [12]

Answer:

$341.07

Step-by-step explanation:

Hanna and Dawson both invested at 3.2% = 0.032

Hannah has balance of 31,000 in account

Dawson has balance of 42000 in account

Interests earned by both are

1)Hannah -P(1+i)^-n

=31000(1+0.032)^-1

=31000(1.032)^-1

=31000(0.968992)

=$30038.752

=$30038.75

Interest earned by Dawson is $31,000 - $30038.75 = $961.25

2)Dawson-  P(1+i)^-n

=42000(1+0.032)^-1

=42000(1.032)^-1

=42000(0.968992)

=$40697.664

=$$40697.664

Interest earned by Dawson is $42,000 - $40697.66= $1302.32

3) Hence the amount that Dawson earns than is:

=$1302.32-$961.25

= $341.07

3 0
3 years ago
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valentinak56 [21]

Answer:

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Step-by-step explanation:

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