Answer:

Step-by-step explanation:




3/4 *7
or
0.75*7
The answer is 5.25
Using the normal distribution, it is found that 25.14% of the batteries will last more than 420 hours.
<h3>Normal Probability Distribution</h3>
The z-score of a measure X of a normally distributed variable with mean
and standard deviation
is given by:

- The z-score measures how many standard deviations the measure is above or below the mean.
- Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.
In this problem, we have that the mean and the standard deviation are given, respectively, by:
.
The proportion of the batteries will last more than 420 hours is <u>one subtracted by the p-value of Z when X = 420</u>, hence:


Z = 0.67
Z = 0.67 has a p-value of 0.7486.
1 - 0.7486 = 0.2514.
0.2514 = 25.14% of the batteries will last more than 420 hours.
More can be learned about the normal distribution at brainly.com/question/24663213
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Right triangles must follow the pythagorean theorem, so a^2+b^2=c^2.
Let's find a^2 and b^2 by squaring the first 2 side lengths.
(x^2-1)^2= x^4-2x^2+1
(2x)^2= 4x^2
Then add the two to find c^2
x^4+ 2x^2 +1= c^2
Root both sides
x^2+1=c
Since the side lengths can be plugged into the pythagorean theorem, the side lengths must represent a right triangle.
Hope this helps!