Question

In a class of 25 students the probability that any one of the 10 girls will be absent on any given day is 0.2. The probability of one of the boys being absent is 0.3 , calculate probability that all the students are present on a Tuesday​

Answer 1

The probability that a girl is absent = 0.2

P(boy is absent) = 0.3

P(girl is present) = 1 - 0.2 = 0.8

P(boy is present) = 1 - 0.3 = 0.7

We want :

P(all students are present) = p(girls are present) and p(boys are present)

= 0.8 × 0.7 = 0.56

= 0.56

Answer 2

Given,

Total students = 25

The probability that any one of the girls will be absent = 0.2

The probability that any one of the boys will be absent = 0.3

To Find,

The probability that all the students are present on a Tuesday​ =?

Solution,

Total students  = 25

Total girls  = 10

Total boys  = 25 - 10 = 15

The probability that any one of the girls will be absent = 0.2

The probability that any one of the girls will be present = 1  - 0.2 = 0.8

Similarly,

The probability that any one of the boys will be present = 1 - 0.3 = 0.7

The probability that all the students are present on a Tuesday​ = 0.8^10*0.7^15

Hence, the probability that all the students are present on a Tuesday​ is 0.8^10*0.7^15