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olasank [31]
3 years ago
13

Can anyone explain to me what this is asking/how to do this? I think it's for the summation formula

et/?f=S_%7Bn%7D%20%3Dn%28%5Cfrac%7Ba_%7B1%7D%2Ba_%7Bn%7D%20%20%7D%7B2%7D%29" id="TexFormula1" title="S_{n} =n(\frac{a_{1}+a_{n} }{2})" alt="S_{n} =n(\frac{a_{1}+a_{n} }{2})" align="absmiddle" class="latex-formula"> but if I'm given a1, an, and n, what are the other numbers for?

Mathematics
1 answer:
disa [49]3 years ago
6 0

Answer:

D 3500

Step-by-step explanation:

This question is asking for the sum of all the terms in an arithmetic series.

So using the formula : Sn = n/2 (a+l) , where Sn is the sum of n terms, a is first term, and l is last term, we try to find Sn, with n being 25, a being 20, and an which is a25 or the twenty fifth term being 260, also being the last term.

Hence we can produce the formula for Sn which is Sn=25/2 (20+260)

Sn=25/2 (280)

=3500

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Write an expression to represent:<br> Nine more than the quotient of two and a number x
Taya2010 [7]

Answer:

9+(2/x)

Step-by-step explanation:

6 0
3 years ago
In a particular faculty 60% of students are men and 40% are women. In a random sample of 50 students what is the probability tha
zimovet [89]

Answer:

a) The expected value is given by:

E(X) = np = 50*0.4 = 20

and the variance is given by:

Var(X) =np(1-p) = 50*0.4*(1-0.4) = 12

b) P(X>25)= 1-P(X\leq 25)

And we can find this probability with the following Excel code:

=1-BINOM.DIST(25,50,0.4,TRUE)

And we got:

P(X>25)= 1-P(X\leq 25)=0.0573

c) 1) Random sample (assumed)

2) np= 50*0.4= 20 >10

n(1-p) =50*0.6= 30>10

3) Independence (assumed)

Since the 3 conditions are satisfied we can use the normal approximation:

X \sim N(\mu = 20 , \sigma= 3.464)

d) P(X>25) = 1-P(Z< \frac{25-20}{3.464}) = 1-P(z

e) P(X>25)= P(X>25.5) = 1-P(X \leq 25.5)

P(X>25)= P(X>25.5) = 1-P(X \leq 25.5)= 1-P(Z

Step-by-step explanation:

Previous concepts

The binomial distribution is a "DISCRETE probability distribution that summarizes the probability that a value will take one of two independent values under a given set of parameters. The assumptions for the binomial distribution are that there is only one outcome for each trial, each trial has the same probability of success, and each trial is mutually exclusive, or independent of each other".

Let X the random variable of interest, on this case we now that:

X \sim Binom(n=50, p=0.4)

The probability mass function for the Binomial distribution is given as:

P(X)=(nCx)(p)^x (1-p)^{n-x}

Where (nCx) means combinatory and it's given by this formula:

nCx=\frac{n!}{(n-x)! x!}

Part a

The expected value is given by:

E(X) = np = 50*0.4 = 20

and the variance is given by:

Var(X) =np(1-p) = 50*0.4*(1-0.4) = 12

Part b

For this case we want to find this probability:

P(X>25)= 1-P(X\leq 25)

And we can find this probability with the following Excel code:

=1-BINOM.DIST(25,50,0.4,TRUE)

And we got:

P(X>25)= 1-P(X\leq 25)=0.0573

Part c

1) Random sample (assumed)

2) np= 50*0.4= 20 >10

n(1-p) =50*0.6= 30>10

3) Independence (assumed)

Since the 3 conditions are satisfied we can use the normal approximation:

X \sim N(\mu = 20 , \sigma= 3.464)

Part d

We want this probability:

P(X>25) = 1-P(Z< \frac{25-20}{3.464}) = 1-P(z

Part e

For this case we use the continuity correction and we have this:

P(X>25)= P(X>25.5) = 1-P(X \leq 25.5)

P(X>25)= P(X>25.5) = 1-P(X \leq 25.5)= 1-P(Z

4 0
4 years ago
Alyssa takes part in the triathlon. She cycles 4/5 of the route, runs 7/8 of the route, and swims the rest of the way. She swims
hjlf

Answer:

12 miles

Step-by-step explanation:

Alyssa takes part in the triathlon. She cycles 4/5 of the route, runs 1/8 of the route, and swims the rest of the way. She swims 0.9 miles. Find the total distance of the triathlon route.

Total distance Alyssa cycled and ran =

\frac{4}{5} + \frac{1}{8}

\frac{32 + 5}{40} = \frac{37}{40}

Distance she swam =  1 - 37/40 = 3/40

3/40 of the distance is 0.9

the total distance = 40/3 x 0.9 = 12 miles

3 0
3 years ago
Evaluate the expressions below for given values
sweet-ann [11.9K]
The answer to the question

8 0
3 years ago
There were 72 runners to start a race. in the first half of the race, 13 of them dropped out. in the second half of the race, 23
Mariana [72]
All you would need to to is do 13+23= 33 to get the total amount of people who dropped out, then do 72 ( the number in the beginning and subtract 33 from it because those are the people who dropped out so 72-33=39. 39 people finished the race.
8 0
3 years ago
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