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Using the mean of the data-set, it is found that the missing height in the stem-and-leaf plot is given by:
D. 65 in.
<h3>What is the mean?</h3>The mean of a data-set is given by the <u>sum of all observations in the data-set divided by the number of observations</u>.
In this problem, following the key of the stem-and-left plot, there are 8 observations, given as follows:
54, 55, 56, 61, 63, 64, 70 and the missing value x.
The mean is of 61, hence:
423 + x = 61 x 8
x = 65.
Hence option D is correct.
More can be learned about the mean of a data-set at brainly.com/question/24628525
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Sum f(k)=4k-10 for k=1 to 18.
We sum each term separately and add the sums.
![\sum_1^{18}4k=4\sum_1^{18}k=4[18(1+18)/2]=4*9*19=684](https://tex.z-dn.net/?f=%5Csum_1%5E%7B18%7D4k%3D4%5Csum_1%5E%7B18%7Dk%3D4%5B18%281%2B18%29%2F2%5D%3D4%2A9%2A19%3D684)
Therefore the required sum is 684-180=504
We sum each term separately and add the sums.
Therefore the required sum is 684-180=504