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aleksandr82 [10.1K]
3 years ago
12

Add first 15 natural numbers and find the average? Solution with formula?

Mathematics
2 answers:
NeTakaya3 years ago
7 0

Good morning ☕️

Answer:

<h2>8</h2>

Step-by-step explanation:

<em><u>the formula :</u></em><em> (sum of 15 consecutive term of an arithmetic sequence)</em>

1+2+3+...+15=\frac{15*(15+1)}{2} =\frac{15*16}{2}=15*8\\

<u><em>Now,</em></u>

Average=\frac{15*8}{15} =8

kicyunya [14]3 years ago
5 0

Answer:

120

Step-by-step explanation:

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-3x-y=-17 4x + 2 y equals 20
ExtremeBDS [4]
-3x - y = -17
4x + 2y = 20

multiply one part of the equation so that we can be able to use the process of elimination.

(-3x - y = -17)2
4x + 2y = 20

Now we have:

-6x -2y = - 34
4x+2y= 20
------------------------
-2x = -14

Divide -2 on both sides.

-2x = -14
/-2       /-2

x = -7.


=============================================

To solve for y, we just have to substitute the value of x to any of the equation given above, that we feel comfortable with. And I'm going to choose this equation: 4x + 2y = 20


4x + 2y = 20

4(-7) + 2y = 20

-28 + 2y = 20

Add 28 on both sides

-28 + 2y = 20
+28          +28
---------------------
2y = 48
/2      /2

y = 24.


The last thing you would do is to check if the answers is correct.
All you have to do is plug in the values of x and y into both equations and see if they equal to one another.

You may have to do this by yourself :P

Anyways, if you have any questions about this topic, feel free to PM me or any other users interested. Thank you for being part of Brainly! Have a nice day!










4 0
3 years ago
Mia is finally able to upgrade her cellphone. The one she wants costs $220 but she is able to get it for 60% off. She has a coup
Kay [80]

The answer would be A) $79.20

(220*.4).9 as 60 percent off means that the product is only 40 percent of its original value, furthermore, we multiply the entire thing by .9


8 0
3 years ago
Write a situation to describe the equation below:<br><br> C=50+16x
kotykmax [81]
Ryan has 50 cookies if he wants to buys x amount of 16 cookies, how many cookies will he have c= cookies
7 0
3 years ago
How much pure acid should be mixed with 6 gallons of a 20% acid solution in order to get a 90% acid solution?
beks73 [17]
So, how much acid is there in 6 gallons?  well is 20% acid or (20/100), so the amount of acid in it just (20/100) * 6 or 1.2, the rest is say water.

now, if we want a 90% solution, and say we add "y" gallons, how much acid is in it?  well (90/100) * y, or 0.9y.

now let's add "x" gallons of pure acid, now, pure acid is just pure acid, so is 100% acid, how much acid is there in it?  (100/100) * x, or 1x or just x.

we know whatever "x" and "y" amounts are, they -> x + 6 = y

and we also know that x + 1.2 = 0.9y

\bf \begin{array}{lccclll}&#10;&\stackrel{gallons}{acid}&\stackrel{acid~\%}{quantity}&\stackrel{acid~gallons}{quantity}\\&#10;&------&------&------\\&#10;\textit{pure acid}&x&1.00&x\\&#10;\textit{20\% sol'n}&6&0.20&1.2\\&#10;------&------&------&------\\\&#10;mixture&y&0.90&0.9y&#10;\end{array}&#10;\\\\\\&#10;\begin{cases}&#10;x+6=\boxed{y}\\&#10;x+1.2=0.9y\\&#10;----------\\&#10;x+1.2=0.9\left( \boxed{x+6} \right)&#10;\end{cases}&#10;\\\\\\&#10;x+1.2=0.9x+5.4\implies x-0.9x=5.4-1.2\implies 0.1x=4.2&#10;\\\\\\&#10;x=\cfrac{4.2}{0.1}\implies x=\stackrel{gallons}{42}
3 0
3 years ago
Assume that the empirical rule is a good model for the time it takes for all passengers to board an airplane. The mean time is 4
slamgirl [31]

Answer:

The interval that describes how long it takes for passengers to board the middle 95% of the time is between 40.16 minutes and 55.84 minutes.

Step-by-step explanation:

Problems of normally distributed samples can be solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the zscore of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

\mu = 48, \sigma = 4.

Which interval describes how long it takes for passengers to board the middle 95% of the time?

This is between the 2.5th percentile and the 97.5th percentile.

So this interval is the value of X when Z has a a pvalue of 0.025 and the value of X when Z has a pvalue of 0.975

Lower Limit

Z has a pvalue of 0.025 when Z = -1.96. So

Z = \frac{X - \mu}{\sigma}

-1.96 = \frac{X - 48}{4}

X - 48 = -1.96*4

X = 40.16

Upper Limit

Z has a pvalue of 0.975 when Z = 1.96. So

Z = \frac{X - \mu}{\sigma}

1.96 = \frac{X - 48}{4}

X - 48 = 1.96*4

X = 55.84

The interval that describes how long it takes for passengers to board the middle 95% of the time is between 40.16 minutes and 55.84 minutes.

7 0
3 years ago
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