For a certain online store, the distribution of number per hour is approximately normal with mean 1200 purchases and standard de
viation 200 purchases. for what proportion of hours will the number of purchases at the online store exceed 1400?
a)5%
b)68%
c)16%
d)32%
a)5%
b)68%
c)16%
d)32%
1 answer:
Answer: 16%
Step-by-step explanation:
When we have a normal distribution, the 100% of our sample will be placed in a "gaussian bell".
Where the middle of this bell coincides with the mean.
The mean, in this case, is 1200, and the standard deviation is 200.
In the image below you can see that between the points.
Mean + standard deviation and the end of the graph, we have:
13.5% + 2.35% + 0.15% = 16%
And particularly, if we want to know the percentage that exceed 1400, will be the same percentage above the mean plus the standard deviation.
mean = 1200
SD = 200
mean + standard deviation = 1200 + 200 = 1400.
Then the percentage that exceeds 1400 is equal to the percentage that we found above, then the correct option is C: 16%
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Like all problems that involve images within the question, we should definitely try to draw this out. In the picture above, I have done this.
Now, we can see that this is just a simple proportion problem. For every 2.5 cm of height of the flower, we are 2 cm from the opening, or aperture. For every 20 cm of height, how far are we? We can set up the problem like this:
20 ............2.5
-------- = ---------
...x ............. 2
where x is the unknown distance to the aperture from the flower. Now, we just need to get x by itself. A typical way of solving something like this is by doing "butterfly multiplication" which is really just a shortcut haha. Anyway, I can rewrite that equation ^ as:
20×2 = 2.5 × x
Then, to solve for x, we would divide both sides by 2.5. (If you don't know why that is, please let me know and I'll elaborate).
We would then have:
20×2
------- = x
2.5
Which then simplifies to:
x = 16
Try using the same logic for your second question, and if you get stuck, I'd be happy to help! please let me know if any of this doesn't make sense. :)
Now, we can see that this is just a simple proportion problem. For every 2.5 cm of height of the flower, we are 2 cm from the opening, or aperture. For every 20 cm of height, how far are we? We can set up the problem like this:
20 ............2.5
-------- = ---------
...x ............. 2
where x is the unknown distance to the aperture from the flower. Now, we just need to get x by itself. A typical way of solving something like this is by doing "butterfly multiplication" which is really just a shortcut haha. Anyway, I can rewrite that equation ^ as:
20×2 = 2.5 × x
Then, to solve for x, we would divide both sides by 2.5. (If you don't know why that is, please let me know and I'll elaborate).
We would then have:
20×2
------- = x
2.5
Which then simplifies to:
x = 16
Try using the same logic for your second question, and if you get stuck, I'd be happy to help! please let me know if any of this doesn't make sense. :)
The picture with the complete question is attached below :
Answer:
In Step 2, 90 should be multiplied by the quantity 10 – 12, not by 10
Step-by-step explanation:
90 * x - 90 * 12 = 90(x - 12)
From the question, x = 10
Hence,
90(10 - 12)
(90* 10) - (90 * 12) - - - > correct evaluation
900 - 1080
= - 180
Hence, both values in the bracket, that is 10 and - 12 should be multiplied by 90. Not just 10 alone.
