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4 years ago

The average of four numbers is 90.Three of them are 138,40,and 102 find the fourth number

Mathematics

2 answers:

Ymorist [56]4 years ago

8 0

Answer:

x=80

Step-by-step explanation:

To find the average, we take the numbers, add them up. Then divide by the number of terms we added.

Let x= the unknown number

The average =90

Average = (138+40+102+x)/4

90 = (138+40+102+x)/4

Multiply by 4 on each side

90*4 =(138+40+102+x)/4 *4

360 = (138+40+102+x)

Combine like terms

360 = 280 +x

Subtract 280 from each side

360-280 = 280+x-280

80 =x

kkurt [141]4 years ago

8 0

<h2>Steps</h2>

So remember that the average formula is $\frac{\textsf{sum of all the numbers}}{\textsf{how many numbers there are}}$ . With the info that we are given, our equation is (Let x = fourth number):

$\frac{138+40+102+x}{4}=90$

From here we can solve for x. Firstly, add up the numerator:

$\frac{280+x}{4}=90$

Next, multiply both sides by 4:

$280+x=360$

Lastly, subtract both sides by 280:

$x=80$

<h2>Answer</h2>

<u>In short, the fourth number is 80.</u>

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3 years ago

What are the values of x and y?

d1i1m1o1n [39]

Answer:

Step-by-step explanation:

y is the value obtained from 4 and 12

y^2 = 4 * 12 Combine

y^2 = 48 Square root both sides.

√y^2 = √48

y = √(3 * 4 * 4)

y = 4√3

Use the Pythagorean Theorem to obtain x

x^2 = y^2 + 4^2

x^2 = 48 + 16

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√x^2 = √64

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Answer

x = 8
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2 years ago

Read the word problem.

Lady bird [3.3K]

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Kip's mother bought 10 bottles.

Word Problem type : multiplication

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4 years ago

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Sales tax = 5%
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⇒ 5% is equal to $2

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5% = $2
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Find 100% (Cost of the meal):
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100% = $0.40 x 100
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Find tips:
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15% tips = 15% x $40
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Find total cost:
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3 years ago

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Alika [10]

Answer:

Step-by-step explanation:

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If a pen's cost IS twice as much as a pencil...

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Now for the money part of this.

The total cost of 11 pens and 11 pencils IS (there's that word again!) 2.10

Therefore,

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But we know from the first expression that pen = 2 pencils so we make the substitution:

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I'm not sure how far you are to go with this. That's the main equation you need to solve this. If you were to go further with it you would distribute the 11 into the set of parenthesis to get:

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33 pencils = 2.10 so

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