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just olya [345]
3 years ago
14

The mean lifetime of a certain tire is 30,000 miles and the standard deviation is 2500 miles. If we assume nothing about the sha

pe of the distribution, approximately what percentage of all such tires will last between 25,000 and 37,500 miles?
Mathematics
1 answer:
kati45 [8]3 years ago
5 0
A standard deviation is 2500 miles, so the range of 25,000 to 37,500 is 2 standard deviations below, and 3 standard deviation above the mean of 30,000. 
We aren't assuming anything about the distribution, but we sort of have to assume a normal distribution in order to answer. When you don't know anything about a distribution, this is generally what you do.
The general rule for standard deviations is:
+/- 1 SD: +/- 34% of population, for a total of 68%
+/- 2 SD: Another 14% in either direction, for a total of 96% of population.
+/- 3 SD, Another 2% in either direction, which pretty much captures the entire distribution (4 standard deviations from the mean is incredibly rare/unlikely) 
We have a range of +/- 1 SD, so we know that 68% percent o the tire 'population' is captured in the range. We also have one more standard deviation in both directions, so we add 28% to this number to get 96% of the population. We have a third standard deviation above the mean, so we add another 2% to arrive at 98% of the population. 

Answer is 98% of all such tires. 
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Answer

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Answer:

  ∠DCF = 129°

Step-by-step explanation:

We assume that line CE is between lines CD and CF.

The angle sum theorem applies:

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borishaifa [10]

Answer:

Biotic, Abiotic

Step-by-step explanation:

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Over time, water vapor in the atmosphere condenses into clouds and eventually falls as precipitation, rain or snow. When precipitation reaches Earth's surface, it has a few options: it may evaporate again, flow over the surface, or percolate—sink down—into the ground.

In land-based, or terrestrial, ecosystems in their natural state, rain usually hits the leaves and other surfaces of plants before it reaches the soil. Some water evaporates quickly from the surfaces of the plants. The water that's left reaches the soil and, in most cases, will begin to move down into it.

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4 0
3 years ago
Joshua's goal is to sell more than 20 items at a farmers' market. So far, he has sold 6 items. Each of his customers buys 2 item
amid [387]

Answer:

More than 7

Step-by-step explanation:

Given that:

Joshua's goal is to sell more than 20 items at a farmer's market.

Number of items already sold = 6

So, number of more items to be sold > Total number of items to be sold - Number of items already sold > 20 - 6 > 14

Given that each customer buys 2 items.

Let c be the number of customers.

So, number of items bought be the customers = Number of items bought by each customer multiplied by the number of customers = 2c

And as per the question statement,

Number of more items to be sold > 14 (as calculated in above step)

2c>14\\\Rightarrow \bold{c>7}

Therefore, the answer is: <em>More than 7 additional customers are required</em>.

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