Eduardo has a red 6-sided number cube and a blue 6-sided number cube. The faces of the cubes are numbered 1 through 6.

Question

Eduardo rolls both cubes at the same time.

The random variable X is the number on the red cube minus the number on the blue cube.

What is P(−2≤X≤1)?

I'm thoroughly vexed with this question. It's not covered in my lessons, and I can't get help with a teacher until tomorrow. If anyone can help, I would majorly appreciate it. Thanks. :)

Answer 1

Just list the possibilities. You know there are 36 total outcomes. How many fit the conditions?
R B R-B
1 1 0
1 2 -1
1 3 -2

2 1 1
2 2 0
2 3 -1
2 4 -2
...
4 6 -2

Then divide the successes by the total of 36

Answer 2

20/36

Answer 3

It's 18/36

Answer 4

A sum of money invested at 7.5% per annum amounts to RS 3920 in 3 years. What will it amount to in 2 years 6 months at 9% per annum?