The work of a student to solve the equation 2(5y − 2) = 12 + 6y is shown below:

1 answer:

8 0

We know that Step 1 is correct, because it is just a restatement of the equation. Therefore, we can eliminate Step 1:

2(5y – 2) = 12 + 6y

In Step 2, the student tried using the Distributive Property. The Distributive Property can be written as one of the two following formulas:

a(b + c) = ab + ac
a(b – c) = ab – ac

In this case, we'll use the second formula. Substitute any known values into the equation above and simplify:

2(5y – 2) = 2(5y) – 2(2)
2(5y – 2) = 10y – 4

In Step 2, the student calculated 2(5y – 2) to equal 7y – 4. However, we have just proven that 2(5y – 2) is equal to 10y – 4.

The student first made an error in Step 2, and the correct step is:

Step 2: 10y – 4 = 12 + 6y

I hope this helps!

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The defect length of a corrosion defect in a pressurized steel pipe is normally distributed with mean value 30 mm and standard d

skelet666 [1.2K]

Answer:

$z=-0.842$

And if we solve for a we got

$a=30 -0.842*7.8=23.432$

So the value of height that separates the bottom 20% of data from the top 80% is 23.432.

Step-by-step explanation:

Let X the random variable that represent the heights of a population, and for this case we know the distribution for X is given by:

$X \sim N(30,7.8)$

Where $\mu=30$ and $\sigma=7.8$

For this part we want to find a value a, such that we satisfy this condition:

$P(X>a)=0.80$ (a)

$P(X$ (b)

As we can see on the figure attached the z value that satisfy the condition with 0.20 of the area on the left and 0.80 of the area on the right it's z=-0.842

If we use condition (b) from previous we have this:

$P(X$