First, I would like to know the differences between the following three scenarios.

```
1. What is the probability that event A or event B occurs?
2. Probability that event A or event B or both occurs?
3. Probability that either event A or event B occurs but not both?
```

Second, A’s annual salary is 60, B’s annual salary is 80.

- A’s annual salary is what percent less than B’s annual salary?
- B’s annual salary is what percent greater than A’s annual salary?

I]

If there are 2 events, you can have -AB, A0, 0B, 00

1 = 3 = A0, 0B

2 = AB, A0, 0B

II]

% less = \frac{B - A}{B} * 100 = \frac{80-60}{80}*100 = \frac{20}{80}*100 = 25

% more = \frac{B - A}{A} * 100= \frac{80-60}{60}*100 = \frac{20}{60}*100 = 33

The denominator is the quantity being referenced “less **than B**” - B goes in denominator

“less **than A**” - A goes in denominator

Thank you. Could you elaborate the first question please? I do not understand AB or A0.

Also are you sure about the denominator in the second question?

AB = Both A and B occurring

A0 = only A occurring

0B = only B occurring

00 = None

So, in 1 and 3 we have A0 and 0B

Where as in 2, we have A0, 0B as well as AB

Yes, the reference thing works for all % changes questions

Profit %, loss %, % more, % less, % increase, decrease

In all these cases, the value being compared to is always at the bottom