# Uniform distrubtion

1. Dec 8, 2011

### jsmith613

1. The problem statement, all variables and given/known data

Questions 3c and 3d

2. Relevant equations

3. The attempt at a solution
ok so for Qc) it must be between 6 and 10 cm from the bottom and 8 and 12 cm from the left

d) it must be within a square 2 cm all the way around the outer full screen

But I don't see how to calculate the answers - there are an infinite number of solutions

Last edited by a moderator: May 5, 2017
2. Dec 8, 2011

### Joffan

Prefacing everything with "Assuming X and Y are independent"... and for extra deviousness, "and that the screen is 20cm x 16cm".

For c), it occupies 1/5 of the horizontal distance and 1/4 of the vertical distance.

For d), take a clue from above and work out the probability of a dot appearing in any 1 cm2 of the screen.

3. Dec 8, 2011

### jsmith613

ok so c) 1/20

d) any 1 cm2 = 1/320
(16*20)-(16*12) = 128
1/320 * 128 = 2/5

is that right?

4. Dec 8, 2011

### Joffan

apart from needing some explanatory text, looks ok

5. Dec 8, 2011

### jsmith613

what explanatory text

6. Dec 8, 2011

### Joffan

To quote the front page of the paper:

You must show sufficient working to make your methods clear to an examiner.
Answers without working will gain no credit.

7. Dec 8, 2011