Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

hi

If I have the 1 circle, 3 triangles and two hexagons and they're in a bag and pick them two times with return what is the probability of getting exactly one hexagon ?

I get 3/9 but the answer is 4/9....

help pls thanks

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

Hi;

4 / 9 is the correct answer.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

Could you explain me how you did it ? I get 12/36 and not 16/36....

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

Hi;

For school problems you should be using the simplest ideas, especially when you are stuck. Did you draw a tree?

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

yes. and what do you mean by simplest ideas ?

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

You always have to get an answer. One way, or the other.

Let me show you how to draw the tree without drawing it:

This is your set of possibilities,

now the triangles and the circle we are not interested in so we give them the generic label of "other." Your set becomes,

the tree looks like this,

oh

ho

oo

hh

do you follow?

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

ok...

explain this

oh

ho

oo

hh

*Last edited by Al-Allo (2013-03-29 11:48:30)*

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

Hi;

oh = ( 4 / 6 ) ( 2 / 6 )

ho = ( 2 / 6 ) ( 4 / 6 )

oo = who cares

hh = who cares

Can you finish that?

**In mathematics, you don't understand things. You just get used to them.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

it gives 16/36

but i still don't understand the logic behind it how did you get those numbers ?ty

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

ho means I drew a hexagon and then something else. The probability of drawing a h is 2 / 6 because there are 2 of them out of the total 6. Then I draw an o, the probability is ( 4 / 6 ) because there are 4 of them out of 6. Same logic for oh.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

i think im gonna re read the problem... im not sure of even understanding what they want ..ty for your help

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

If you are not sure of the problem then please just copy it over here.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

Here :

An aleatory experience consists of turning an arrow on a roulette two times. (3 triangles, 1 circle, and two hexagon)

Question : What is the probability of obtaining exactly one haxagon.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

The question is the same as the one you posted in post #1. The answer and logic are the same, 4 / 9. I can draw a tree if it will help.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

Yes, please. !

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

Here is the full tree do you know what to do from here? Pay no attention to the numbers after the words circle triangle or hexagon.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

anyway, ill go through what you posted tomorrow, i dont have the energy tonight to think about it. thanks for your efforts to help.*curiously, when you get stuck on problems, how do you operate to solve them? any principles,etc. ?

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

For probability and combinatorics when stuck I do it the hard way. No calculations, draw trees or count them all by hand.

**In mathematics, you don't understand things. You just get used to them.**

Offline