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Ivanshal [37]
1 year ago
15

1. A notebook costs $5 more than a folder. Greg purchased 3 notebooks and 2 folders and paid a total cost $30. What is the cost

of each item? 1. A notebook costs $ 5 more than a folder . Greg purchased 3 notebooks and 2 folders and paid a total cost $ 30 . What is the cost of each item ?​
Mathematics
1 answer:
stiv31 [10]1 year ago
8 0
Answer
Notebook each =$4
Folder each = $9

First we write out what we know
Notebook = n
Folder = f
It says a notebook is +5 than a folder so
f = n +5
It says he bought 3 notebooks and 2 folders for $30
3n + 2f = 30

Because we know from the first equation
f=n+5, we can substitute that into the second equation for f

3n + 2(n+5) = 30
3n + 2n +10 =30. Now Combine like terms
5n +10 =30. Now isolate n by subtracting 10 from both sides
5n = 20. Now isolate n by dividing both sides by 5
n = 4

Now we do the same thing to find f
We substitute the value of n (4) into the equation 3n + 2f =30
3(4) +2f =30
12 +2f =30. Now isolate f by subtracting 12 from both sides
2f = 18. Now isolate f by dividing both sides by 2
f = 9


We check our work by inserting the n and f values we found into one of the equations
n + 5 = f
4 + 5 = 9
9 = 9. It worked it equals so it’s correct
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The pH of a solution is measured eight times by one operator using the same instrument. She obtains the following data: 7.15, 7.
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(b)0.000371

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Step-by-step explanation:

We are given the following sample data.

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(x - mean)²/n - 1

n = 8

Sample variance = (7.15 - 7.185)² + (7.20-

7.185)²+ (7.18 -7.185)² + (7.19 -7.185)² + (7.21 - 7.185)² + (7.20 - 7.185)² + (7.17 - 7.185)² + (7.18 - 7.185)² /8 - 1

= 0.001225 + 0.000225+ 0.000025+ 0.000025 + 0.000625 + 0.000225 + 0.000225 + 0.000025/7

= 0.0026/7

= 0.000371428571

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= √0.000371428571

= 0.01927248223

To 3 decimal places = 0.019

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