You are Here: Home >< Maths

# Probability - help needed Watch

1. Hi,

I'm kinda stuck on the folllowing question:

If events A and B are such that P(A) = 0:3, P(B) = 0:4 and P(A n B) = 0:1, what
is the probability that at least one event will occur?

My answer is 0.7. The probability that at least one occurs is P(A or B) + P(A and B) if I'm correct. So that is P(A) + P(B) - P(A and B) + P(A and B)??

Thanks
Hi,

I'm kinda stuck on the folllowing question:

If events A and B are such that P(A) = 0:3, P(B) = 0:4 and P(A n B) = 0:1, what
is the probability that at least one event will occur?

My answer is 0.7. The probability that at least one occurs is P(A or B) + P(A and B) if I'm correct. So that is P(A) + P(B) - P(A and B) + P(A and B)??

Thanks
You've got things a bit mixed up...

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

I've even found you a picture to help visualise this:

So the correct answer, which I'm sure you can work out now, is 0.6

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: December 24, 2010
Today on TSR

### Degrees to get rich!

... and the ones that won't

### Women equal with Men?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.