Answer:
16.4 million viewers
Step-by-step explanation:
The number of viewers increased by 8 million from 10 to 18 million when the number of ads increased by 10 ads from 15 to 25. If 23 ads are run, that represents an increase of 8 ads from 15, so we expect 8/10 of the increase in viewers.
8/10 × 8 million = 6.4 million
The number we expect with 23 ads is 6.4 million more viewers than 10 million viewers, so is 16.4 million.
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<em>Alternate solution</em>
We can write a linear equation in 2-point form for the number of viewers expected for a given number of ads:
y = (18 -10)/(25 -15)(x -15) +10
y = (8/10)(x -15) +10
y = 0.8x -2 . . . . . million viewers for x ads
For 23 ads, this gives ...
y = 0.8×23 -2 = 18.4 -2 = 16.4 . . . . million viewers, as above
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<em>Comment on 8/10</em>
I consider it coincidence that the number 23 is 8/10 of the difference between 25 and 15, and the slope of the line is 8/10. The point we're trying to interpolate has no relationship to the slope of the line, and vice versa.
