to ask if you can answer a question re probability (Maths question)

[Fainne]

So, say I have 20 cards in a pack.

I pick one. It's the Ace of Diamonds let's say for argument's sake.

I then pick another one out of the same pack of 20 cards the following day.

Am I correct in saying that the odds of me picking the same card is a multiple of the single odds?

So 1/20 x 1/20 = 1/400

?

Because I've someone telling me the odds are still 1/20 that I'll pull the same card.

Fainne

Nobody cares about your religious habits. Stop drinking and posting.

So you guys can't work it out so you claim I'm drunk? PMSL!

God - the English education system has a LOT to answer for.

But, if any of you wish to play poker - I'll happily host!

I’ll try again...

Try this.
I have two dice that I roll at the same time.

1. What is the probability that they both show a six?
2. What is the probability that they will both show the same number?

FFS we hear about the great British Education system. This is basic maths ffs!

OP there are two different questions in your posts.
The odds of picking ace of diamonds two days in a row is 1/400. As you say, it's multiplying the single odds.
Once you've got the ace of diamonds on the first day the odds of picking the ace of diamonds the next day is 1/20 (one lot of the single odds).

1. 1/36
2. 1/36 with a little 5 on top of the six which I can't do on my laptop.

If it’s such basic maths, how about trying the simple question I set? You can probably find the answers on google if it’s too hard.

Mate, I've worked out the probabilities of several questions now, and so has Purple. The problem is you can't decide what your question is or, possibly, read.

If your desired outcome is very narrow, as in you need to draw a particular individual card twice, and only that card will do out of all 20, then your odds are 1/400 before you start.

If you have wider criteria, and any card out of that 20 , so long as you get it twice, then the odds are 20/400, which equals 1/20.

The question is about picking the same card two days in a row. I had to simplify it. I suspect I complicated things.

The odds of you picking the same card 2 days running is 1 in 20.

The odds of you picking a pre-selected card two days running is 1 in 400.

1. 1/36
2. 1/6

Sad times.

1. 1/36
2. 1/36 with a little 5 on top of the six which I can't do on my laptop.
Ouch.

Jesus

You're all making this far too complicated. My head hurts.

Basically, if you don't specify which card you want on day 1 there are no odds to beat are there? So the only thing that counts is day 2 when you want the same card you picked on day 1. Art this point you have a 1/20 chance.

On the other hand, if you specify you want the Ace of Spades or whatever then the odds become 1out of 20 you will pick that card. You replace it, and the next day you try to pick it again - you are now in the same position you were in in the first scenario, looking for the card you picked yesterday, so 1 / 20 chance. So in scenario b, 2 lots of 1 in 20 make ....1 in 400. Simples!

No - the question was quite clear. What are the odds of picking the same card two days running.

1/36 with a little 5 on top of the six which I can't do on my laptop.

Okay, now we're getting to the root of the problem. Right, we can sort this misunderstanding out.

Be right back, I need to draw a tree diagram to illustrate this one.

The question is about picking the same card two days in a row. I had to simplify it. I suspect I complicated things.
So its 1 in 20.

Assuming there's no prospect you might accidentally slip, miss the deck and fail to pick a card on day 1, there is a 100% probability you will pick a card on day 1.

The odds of you picking the same card the next day are 1 in 20.

So...its 1 in 20.

This will blow your mind.

I have written out all 36 possibilities for he numbers the two dice could display. I have circled the ones with matching numbers (two 1s, two 2s etc).

There are 6 sets of matching numbers. There are 36 possibilities.

6/36 = 1/6

Can you now see that if you don’t specify which card you need on both days the probability of two matching cards increases from 1/400 to 1/20?

PMSL. You guys really don't do maths do you?

Okay, it's a troll.

Purple - could you and your sideways numbers, do one please?

"The question is about picking the same card two days in a row."

Then the answer is 1/20.

There are 400 possible combinations of two cards and 20 of those are the same card twice. 20/400 = 1/20

Have I made your head hurt Spamantha?

Here we are with the being aggressive when you are shown to be wrong.

Good Lord - you get worse with every post!