Answer:
Mean track length for this rock specimen is between 10.463 and 13.537
Step-by-step explanation:
99% confidence interval for the mean track length for rock specimen can be calculated using the formula:
M±
where
- M is the average track length (12 μm) in the report
- t is the two tailed t-score in 99% confidence interval (2.977)
- s is the standard deviation of track lengths in the report (2 μm)
- N is the total number of tracks (15)
putting these numbers in the formula, we get confidence interval in 99% confidence as:
12±
=12±1.537
Therefore, mean track length for this rock specimen is between 10.463 and 13.537
To find what the number is, we need to set up proportional fractions.
Currently, we have 8% of a number is 20.
To set up our fractions, put 100% under 8% as a fraction first.
It should look like this: 8/100 (hint: per-cent means per-hundred).
Now, we have 20 out of a number, x. This is because we are claiming that 20 is 8% of a number (if we just reword the question without changing the concept).
It should look like this: 20/x.
Our proportional fractions are:
20/x = 8/100.
To solve for this, we need to cross-multiply the denominator of 8/100 (bottom number, 100) with the numerator of 20/x (top number, 20).
This product equation should look like this:
20 x 100 (when simplified, we get 2000).
Now, we need to cross multiply the numerator of 8/100 (top number, 8) with the denominator of 20/x (bottom number, x).
This product equation should look like this:
8x.
Now that we've cross-multiplied, set our two products as an equation.
8x = 2000.
To solve for x, divide both sides by 8 (remember, what you do to one side of an equation, you must do it to the other).
8x / 8 = x
2000 / 8 = 250.
x = 250
Your final answer is:
8% of 250 is 20.
I hope this helps!
Answer:
20400
Step-by-step explanation:
its 2.03x10x10x10x10 so first ten: 20.4 and ten: 204 3rd ten: 2040 last ten :20400
Answer:
I believe it is 21
Step-by-step explanation:
