Rewrite all the numbers as decimals:
14/5 = 2.8
2.6 is already a decimal
2 1/8 = 2.125
2.8 is the largest number so rob is closest to being finished.
Answer:
0.8413 = 84.13% probability of a bulb lasting for at most 605 hours.
Step-by-step explanation:
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean
and standard deviation
, the z-score of a measure X is given by:

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
The standard deviation of the lifetime is 15 hours and the mean lifetime of a bulb is 590 hours.
This means that 
Find the probability of a bulb lasting for at most 605 hours.
This is the pvalue of Z when X = 605. So



has a pvalue of 0.8413
0.8413 = 84.13% probability of a bulb lasting for at most 605 hours.
5 feet is equal to 60 inches. 60 inches divided by 2.5 inches per hour means it would take 24 hours for the drill to reach five feet (assuming it maintains the same rate of digging)
3s + h = $47
7s + 2h= $107
3s + h =$47
3s - 3s + h = $47 -3s
h = $47 - 3s
7s + 2($47 - 3s) = $107
7s + 94 -6s = 107
s + 94 = 107
s +94 -94 = 107- 94
s = 13
3(13) + h = $47
39 + h =$47
39 -39 + h= $47-39
h = 8
Check
7s + 2h= $107
7(13) + 2(8)= $107
91 + 16= 107
107 = 107
She earns $13 per suit sold and $8 per pair of shoes sold.