Answer:
-2.25
Step-by-step explanation:
9(1-x) = 27Y
9-9x =27y
-9x -27y = -9 multiply all terms by -1
9x +27y =9 equation (1)
x-y= -11/2 equation (2)
by solving 2 equations
x= -3.875
y= 1.625
∴ x+ y = 1.625 +(-3.875) = -2.25
Answer:
(E) 0.71
Step-by-step explanation:
Let's call A the event that a student has GPA of 3.5 or better, A' the event that a student has GPA lower than 3.5, B the event that a student is enrolled in at least one AP class and B' the event that a student is not taking any AP class.
So, the probability that the student has a GPA lower than 3.5 and is not taking any AP classes is calculated as:
P(A'∩B') = 1 - P(A∪B)
it means that the students that have a GPA lower than 3.5 and are not taking any AP classes are the complement of the students that have a GPA of 3.5 of better or are enrolled in at least one AP class.
Therefore, P(A∪B) is equal to:
P(A∪B) = P(A) + P(B) - P(A∩B)
Where the probability P(A) that a student has GPA of 3.5 or better is 0.25, the probability P(B) that a student is enrolled in at least one AP class is 0.16 and the probability P(A∩B) that a student has a GPA of 3.5 or better and is enrolled in at least one AP class is 0.12
So, P(A∪B) is equal to:
P(A∪B) = P(A) + P(B) - P(A∩B)
P(A∪B) = 0.25 + 0.16 - 0.12
P(A∪B) = 0.29
Finally, P(A'∩B') is equal to:
P(A'∩B') = 1 - P(A∪B)
P(A'∩B') = 1 - 0.29
P(A'∩B') = 0.71
