Question

there are 27 students in chemistry class and 22 students in physics class,seven of these students take physics and chemistry.what is the ratio of the number of students taking only physics and chemistry.

Answer 1

We can answer these questions from Venn diagrams :

a) Two classes meet at the same hour :

n(C∩P) = n(C) + n(P)

n(C) = 20

n(P) = 30

= 20 + 30 = 50

b)when two classes meet differently

n(C∪P) = n(C) + n(P) - n(C∩P)

n (C∩P) = 10

= 20 + 30 - 10 = 40

Answer 2

Step-by-step explanation:

27+22-7=42 now 42-27=15 and42-22=20.so required ratio=15:20=3:4