# Probability problem 2

#### susumandrai

##### New member
I have no idea how to start doing this problem:

John wants to have the roof of his house painted. He has the choice of three roof painters: Paintfast, Quickpaint and Rapidpaint. After making extensive enquiries, he establishes that the probabilities of the painters doing the job satisfactorily are 0.85, 0.75 and 0.6 respectively. Each painter offers to return in one year’s time and repair any unsatisfactory work. The probabilities that the repair job will be satisfactory are 0.85, 0.95 and 0.9 respectively. John then checks with each painter’s bank manager, and is told that the probabilities that each one will still be in business in one year’s time are respectively 0.5, 0.7 and 0.8.
John intends to sell his house in two years’ time, and it is most important to him that the roof be in good order.
a Which painter should John choose to paint his roof?
b What is the probability that, if this painter is chosen, John is able to sell his house with the roof in good order?

text book says answers are:
a. quickpaint
b. 0.91325

#### Subhotosh Khan

##### Super Moderator
Staff member
I have no idea how to start doing this problem:

John wants to have the roof of his house painted. He has the choice of three roof painters: Paintfast, Quickpaint and Rapidpaint. After making extensive enquiries, he establishes that the probabilities of the painters doing the job satisfactorily are 0.85, 0.75 and 0.6 respectively. Each painter offers to return in one year’s time and repair any unsatisfactory work. The probabilities that the repair job will be satisfactory are 0.85, 0.95 and 0.9 respectively. John then checks with each painter’s bank manager, and is told that the probabilities that each one will still be in business in one year’s time are respectively 0.5, 0.7 and 0.8.
John intends to sell his house in two years’ time, and it is most important to him that the roof be in good order.
a Which painter should John choose to paint his roof?
b What is the probability that, if this painter is chosen, John is able to sell his house with the roof in good order?

text book says answers are:
a. quickpaint
b. 0.91325
Find the probability of each painter:

doing good job + Doing badjob (but doing good repair + be in business to fix)

However for the part 'b' I get 0.91625

#### susumandrai

##### New member
Find the probability of each painter:

doing good job + Doing badjob (but doing good repair + be in business to fix)

However for the part 'b' I get 0.91625
Thank you Subhotosh. I have got it now. Sorry The answer in the text book says .91625 - i think i had a typing mistake.
Thank you so much.

I also started a thread Probability Problem 1. Can you help me in that as well.

Many thanks....