In a certain class of students, there are 11 boys from wilmette, 7 girls from wilmette, 5 boys from winnetka, 4 girls from winnetka, 4 boys from glencoe, and 4 girls from glencoe. if the teacher calls upon a student to answer a question, what is the probability that the student will be a boy

Probability that a boy will answer the question =

Step-by-step explanation:

In a certain class of students,

Number of boys from Wilmette = 11

Number of boys from Winnetka = 5

Number of boys from Glencoe = 4

Total boys in the class = 11 + 5 + 4 = 20

Similarly, total number of girls in the class = 7 + 4 + 4 = 15

Total number of students in the class = 20 + 15 = 35

Now number of ways we can choose 1 boy out 20 boys

=

Similarly number of ways, we can choose a boy out of 35 students =

Now the probability that a boy will answer the question =

=

(b) 240

step-by-step explanation:

first, we use the pythagorean formula using the given side lengths to find x. then we use x to find the side lengths. then we add the side lengths to find the perimeter.

pythagorean theorem formula:

a^2 + b^2 = c^2

(x - 20)^2 + (x - 40)^2 = x^2

x^2 - 40x + 400 + x^2 - 80x + 1600 = x^2

x^2 -120x + 2000 = 0

(x - 100)(x - 20) = 0

x - 100 = 0 or x - 20 = 0

x = 100 or x = 20

we see that the solution x = 20 must be discarded because it will give a negative side length and a side length of 0. the only valid solution is x = 100.

perimeter = sum of the lengths of the sides

perimeter = x + x - 20 + x - 40

perimeter = 3x - 60

replace x with 100.

perimeter = 3(100) - 60

perimeter = 300 - 60

perimeter = 240

they charge the same amount at 20 minutes.

step-by-step explanation: