Question

Helena has an 80% chance and Rodriquez has a 50% chance of obtaining 'A' grades in their History examination. Find the probability that:

a both will obtain 'A' grades
b Rodriquez will get an 'A' and Helena will not
c.neither will obtain 'A' grades.
​

Answer 1

a) 0.40

b) 0.10

c) 0.60

Explanation:

Helena has 80% chance of getting A ,

`P(A_H) = (80)/(100) = 0.80`

Rodriquez has 50% chance of getting A ,

`P(A_R) = (50)/(100) = 0.50`

a)

`P(A_H A_R) = P(A_H) * P(A_R) = 0.80 * 0.50 = 0.40`

b)

`Probability \ Helena \ will \ not \ get \ A\ , \ P(A_H^(') ) = 1 - P(A_H) = 1 - 0.80 = 0.20`

Probability Rodriquez will get A and Helena will not

`P(A_RA_H^('))` = 0.50 x 0.20 = 0.10

c) Probability neither will obtain A = 1 - Probability both will get A

= 1 - 0.40

= 0.60