simple questions

[Salvadoramerican]

[unparseable or potentially dangerous latex formula]. Find p+q+r

Ma Bell's telephne company assigns 10 digit phone numbers. What are the odds that the last digit of a randomly chosen phone number is 9 or 0?

[Salvadoramerican]

Can someone answer please

[BlasianAsian]

Alright, I can do the second one.

So...10 digits.

Last one has to be a 9 or a 0.

It always helps to make a list in probability problems.

10 digits: __ __ __ __ __ __ __ __ __ __

Last on is 9 or 0

__ __ __ __ __ __ __ __ __ 9

__ __ __ __ __ __ __ __ __ 0

And the other digits can be anything:

So:

[unparseable or potentially dangerous latex formula], in essence.

This is out of: [unparseable or potentially dangerous latex formula] Choices. Then you have:

[unparseable or potentially dangerous latex formula]

Calculated: [unparseable or potentially dangerous latex formula]

Same answer? WTF?

[88bobcat]

[88bobcat]

[BlasianAsian]

Oh. Forgot. =D

What do you mean by finite set? ????

[007math]

Both your answers are the same.....if you convert the 1/5 into odds (since he said that was the probability) you get 1/4.

I'm getting 1/4 odds myself whether you repeat digits or not so it doesn't seem to matter in the final answer. Although, has anyone seen a phone number that starts with "0"?

Heh, I actually remember doing this question a long time ago. I had done it both ways on the test...

[BlasianAsian]

Wow. So I changed it to suit BobCat88...and got the same answer. No, I mean the first time, I got a giant bamboobalized fraction, which somehow equated into 1/4, and when I changed it to where you could use all ten digits for every digit space, I got a cleaner fraction, which still equaled 1/4. Hmm...lucky! =D

[nsguy1350]

1/4 sounds right to me. What does the answer key say?
Also, I would bet that phone numbers such as 037-962-3458, with the zero first are excluded, but this changes nothing, answer-wise.

[Salvadoramerican]

thanks