x Turn on thread page Beta
 You are Here: Home >< GCSEs

# Maths probability question help watch

1. On any school day, the probability that Josh oversleeps is 1/5. If he oversleeps, the probability that he will remember all his books is 2/9. If he does not oversleep, the probability that he will remember all his books is 5/7. Use a tree diagram to work out the probability that Josh will not remember all his books tommorow.
2. (1/5*7/9) + ( 4/5 *2/7)
3. okay you need to draw out a tree diagram so i would draw one out with both routes because it won't let me draw one. You need to have two columns with the first one being oversleeps then yes/no, then the second being remember books yes/no for both of the first outcomes (so you will end up with a yes/no then from the yes a yes/no and from the no a yes/no

Once you have done this, you need to follow both the routes (Yes Yes) and (No Yes) and you have to add them because you're working out an 'or' so the probability of either occouring. So, it could be Yes Yes (1/5 * 2/9 = 2/45) or No Yes (4/5 * 5/7)= 20/35 (this cancels to 4/7, which is equivalent to 36/45)

You then add the two probabilities together to make 38/45.

hope this helped
4. (Original post by jaspreetb)
On any school day, the probability that Josh oversleeps is 1/5. If he oversleeps, the probability that he will remember all his books is 2/9. If he does not oversleep, the probability that he will remember all his books is 5/7. Use a tree diagram to work out the probability that Josh will not remember all his books tommorow.
(probability of him oversleeping and forgetting his books) + (probability of him waking up on time and forgetting his books)

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: April 23, 2016
Today on TSR

### Any tips for freshers...

who are introverts?

### More snow?!

Discussions on TSR

• Latest
Poll
Useful resources

## Study tools

### Essay expert

Learn to write like a pro with our ultimate essay guide.

See where you can apply with our uni match tool

### Make study resources

Create all the resources you need to get the grades.

### Create your own Study Plan

Organise all your homework and exams so you never miss another deadline.

### Resources by subject

From flashcards to mind maps; there's everything you need for all of your GCSE subjects.

### Find past papers

100s of GCSE past papers for all your subjects at your fingertips.

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

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