Your picture has several issues.
- x is not defined. It appears to be the number of apartments rented.
- R(x) is defined two different ways. The first way, it looks like it is the revenue from a single apartment. The second way, it looks like it is the revenue from the entire apartment complex.
- The derivative is in error. It should be -20x +2000. In any event, this is not the derivative you want. You're not trying to maximize revenue; you're trying to maximize profit.
- It might be useful to write an equation for profit: P(x) = R(x) -200x = -10x² +1800x. Then when you go to maximize it, your derivative will be P'(x) = 0 = -20x +1800 ⇒ x = 90.
Your answer is correct, but the path you followed to get there has a few potholes.
The answer is B, because 44 is greater than 42. I hope this helps!
According to his calculations, b has a 3/10 chance to win
That's false.
For similar triangles, corresponding angles are congruent.
Corresponding sides are in the same ratio but rarely congruent.
(They're congruent only if the ratio is ' 1 ', i.e. the triangles are congruent
as well as being similar.)
