Question

Student in a highschool can choose to study spanish and french as a foriegn language.In a given academic year, 90%of pupils choose spanish and the rest choose french.30%of the student who are learning spanish are boys and 40% of who are studying french also boy. If student was randomly selected from this academic year, What is the probability that it would be

a) a girl?

b) What is the probablity selected boy student given that spanish language study?

c) A boy?

d) what is the probability that a randomly selected student is a boy or somebody who studies french?

e) whay is the probability that randomly selected student is girl who does not study french?

Answer 1

a)

$P=0.9\cdot0.7+0.1\cdot0.6=0.69$

b)

in class of spanish 30% are boys

so:

$P=0.3$

c)

$P=0.9\cdot0.3+0.1\cdot0.4=0.31$

d)

$P=0.31+0.1-0.1\cdot0.4=0.37$

e)

90%of pupils choose spanish where 70% are girls

so:

$P=0.9\cdot0.7=0.63$