Answer:
<h2>
<em><u>38</u></em></h2>
Step-by-step explanation:
She began with 38 books.
28 - 9 = 19
19(2) = 38
Hope this helps!
Here's what I did which might help you
Answer:
n=206
Step-by-step explanation:
Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The population proportion have the following distribution
Solution to the problem
In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 99% of confidence, our significance level would be given by
and
. And the critical value would be given by:
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that
, we can use as prior estimate of p 0.5, since we don't have any other info provided, and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
And replacing into equation (b) the values from part a we got:
And rounded up we have that n=206
it take him 90 hrs to plow 60 acres
For this example, we must combine not permutate; this because a salad in which you first use apple then tomato is the same as the one in which you use first tomato then apple, so order does not matter.
Me must do "10 combine 7" which is written by the binomial coefficient

; in general a binomial coefficient is written by:

In which

and

are positive integers, such that

.
So, for this problem:
Hence, there are 120 different ways to make the fruit salad.