Posted by **martha** on Wednesday, June 6, 2012 at 5:44pm.

Nine cards are numbered 1-9. what is the probability of drawing a number greater than 6 or an odd number.

I know the answer is 2/3 but I don't know how you find the probability when it says "greather than 6 OR and odd number"... how do you calculate the OR?

- math -
**Count Iblis**, Wednesday, June 6, 2012 at 6:01pm
You can rewrite this such that the "OR" applies to mutually exclusive possibilities, and then you can add up the proababilities.

The probabilitity of drawing an odd number or a number larger than 6, is the same as drawing one of the odd numbers smaller than 6, or a number larger than 6. The OR now refers to mutually exclusive possibilitities and you can then add up the probabilities for them as there is no double counting.

Clearly there are 6 numbers that satisfy the criterium, so the probablity is 6/9 = 2/3.

YOu can also handle "OR" diurectly using the principle of exclusion and inclusion using the formula:

N[A OR B] = N[A] + N[B] - N [A AND B]

There are 3 numbers larger than 6, there are 5 odd numbers and there are 2 numbers that are larger than 6 nd odd. There are thus 3 + 5 - 2 = 6 numbers that are larger than 6 or odd.

## Answer this Question

## Related Questions

- Algebra probability - Helena has a set of number cards numbered 1 thru 10. If ...
- maths - Some cards are numbered from 1 to 30. They are reshuffled and arranged. ...
- math - I MUST DRAW TWO CARDS WHOSE SUM IS NINE, FROM A STACK OF CARDS NUMBERED ...
- math - cards numbered 0 through 9 are in a bag. what is the probability you pull...
- Math - A nickel is flipped and a dime is flipped. 1. What is the probability of...
- Probability - A nickel is flipped and a dime is flipped. 1. What is the ...
- 7th grade math (probability) - Can you check these, please? Ten cards numbered 1...
- Statistics - a roulette wheel has 40 slots evenly divided between red (even) and...
- Bloemhof Gekombineerde Skool - Twenty cards are numbered from 1 to 20. The cards...
- stats - a box contains 100 cards, of which 25 are numbered 1, 35 are numbered 2...

More Related Questions