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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Answer:
Step-by-step explanation:
length = 25 in
Perimeter = 86 in
2*(length + width) = 86
2*(25 + N) = 86
Divide both sides by 2
25 + N = 86/2
25 + N = 43
Subtract 25 from both sides
25 + N - 25 = 43 - 25
N = 18
In order to obtain a ratio of boys to girls equal to 3:5, the number of boys has to be written as 3 x and the number of girls as 5 x where x is a common factor to the number of girls and the number of boys. The total number of boys and girls is 600. Hence
<span>3x + 5x = 600 </span>
Solve for x
<span>8x = 600 </span>
<span>x = 75 </span>
Number of boys
<span>3x = 3 × 75 = 225 </span>
Number of girls
<span>5x = 5 × 75 = 375</span>