The first standard deviation covers about 68% of the distribution in a normal curve. (34% higher, 34% lower than the mean). the second standard deviation covers 28% (14% between 1st and 2nd SD above the mean, 14% between 1st and 2nd SD below the mean). In our case
1 Standard deviation = 27 hours (we will approximate to 25 hours)
Mean = 2,000
This means that 34% of the distribution is between 1975 and 2000 hours (within 1 standard deviation below the mean)
2,000- 2,050 covers the range within 50 hours above the mean.
50 hours is roughly 2 standard deviations. The second standard deviation (standard deviation between 1 and 2) covers around 14% on each side of the distribution.
50 hours is roughly 2 standard deviations, which means we add 34% + 14% = 48%.
The range of 1,975 - 2,050 hours covers 34% of the distribution below the mean and 48% of the distribution above the mean.
This means that the probability that the light bulb will last somewhere within this range is 34% + 48% = 82%
The closest answer is 79%. The difference can be explained by the fact that, for simplicity, we approximated the standard deviation to be ~25 hours instead of the real standard deviation of 27 hours.
Answer:
1/6
Step-by-step explanation:
There are 12 numbers in total. There is a 2 on each cube so there are two possible chance. 2/12=1/6 2/2=1 and 12/2=6 therefore 2/12=1/6
Answer:
On Tuesday
3/4 + 3/4 = 3/2 = 1 1/2 = 1.5
On Wednesday
2/4 + 1 1/4 = 7/4 = 1 3/4 = 1.75
Then we subtract
1.75 - 1.5 = 0.25
9514 1404 393
Answer:
20
Step-by-step explanation:
Let n, d, q represent the numbers of nickels, dimes, and quarters, respectively. Then we have ...
n + d + q = 45
5n +10d +25q = 700
n -d = -5
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Using n=d -5, we can substitute into the first two equations:
(d -5) +d + q = 45
2d +q = 50 . . . . add 5, collect terms [eq4]
__
5(d -5) +10d +25q = 700
15d +25q = 725 . . . . . . . . . . add 25, collect terms [eq5]
Multiplying [eq4] equation by 3 and subtracting that from 2/5 of [eq5], we have ...
(2/5)(15d +25q) -3(2d +q) = (2/5)(725) -3(50)
6d +10q -6d -3q = 290 -150
7q = 140 . . . . . . simplify
q = 20 . . . . . . . . divide by 7
There are 20 quarters.
unwillingness or disinclination to do something.
or: the property of a magnetic circuit of opposing the passage of magnetic flux lines, equal to the ratio of the magnetomotive force to the magnetic flux