Question

Use the equation P(A or B)= P(B)-P(A and B) to find the missing value below.

P(A)=1/3
P(A and B)=1/8
P(A or B)= 3/4
Find P(B)=____(Please submit your answer as the lowest term fraction)

Answer 1

`P(B) = (7)/(8)`

Explanation:

Given

P(A or B)= P(B)-P(A and B)

P(A)=1/3

P(A and B)=1/8

P(A or B)= 3/4

Required

Find P(B)

To find P(B), all we need to do is to substitute values of P(A or B) and P(A and B) in the given equation.

This goes thus;

P(A or B) = P(B) - P(A and B) becomes

`(3)/(4) = P(B) - (1)/(8)`

Make P(B) the subject of formula

`P(B) = (3)/(4) + (1)/(8)`

Take L.C.M

`P(B) = (6 + 1)/(8)`

Add fractions

`P(B) = (7)/(8)`

From the workings above, the value of P(B) using the given equation is
`(7)/(8)`