Giving a test to a group of students, the grades and gender are summarized below Male
Female
Total
A
13
5
18
B
9
4
13
С
20
3
23
Total
42
12
54
If one student is chosen at random,
Find the probability that the student was NOT a male that got a "C"

Perimeter = 35
2(L + W) = 35
L + W = 35/2
w = 35/2 - L

Area(A) = L * W
= L(35/2 - L)
A = (35/2)L - L^2

When Length = 13 cm (Say, L1)
Area = 58.5 cm^2 = A1

When Length = 16cm (Say, L2)
Area = 24 = A2

Average rate of decrease of Area = (A2 - A1)/(L2 - L1)
= -11.5 cm^2 / cm