## Your Questions About Odd Calculator

Carol asks…

## If I had a container filled with 10 coke 8 sprite and 7 rootbeer what are the odds of choosing 3 sprite?

Choosing 3 sprite from the container all at the same time.

Choosing 3 sprite all at once without looking in the container.

### admin answers:

First, we’ll make some fairness assumptions. Let’s say that all the containers are the same size and shape as each other so the chance of blind grabbing one container is the same as the chances of blind grabbing one of the other containers instead. And I’ll assume too that you are blind grabbing, not being guided by reading the labels. And that the containers are thoroughly randomized in the bucket. And no one else is adding or subtracting containers from the bucket during the experiment.

I assert that reaching in with both hands and blind grabbing 3 containers at once is the same as reaching in 3 times and blind grabbing one container each time, so long as you don’t put back (that is „reject“) a container before you’ve gotten 3 containers.

On the first grab, there are 10+8+7 containers (I’ll just saw „cans“) and 8 of them are sprite.

For the first can pulled out, the odds of it being a sprite are 8/25. If the first can was a sprite, the odds of the 2nd can being a sprite are 7//24. If can 1 & 2 were sprite, the odds of the 3rd can being a sprite are 6/23. So the odds of hitting a sprite trifecta are (8/25)*(7/34)*(6/23), which by my calculator works out to just over .017, which means the chances of randomly accomplishing this feat are less than 1 chance in 50. Not like the odds against hitting the mega-millions lottery,, but still not very likely an event to happen.

The good news, assuming you like sprite, is that the odds of not getting any sprite at all in your first 3 draws is only like 1 in 3. That is, 2 out of 3 times of trying a 3-can experiment, at least one of the first 3 cans drawn is going to be a sprite. I’ll leave the arithmetic and details up to you..

Joseph asks…

## Urgent help with my fx991ES PLUS CASIO calculator? I need to know how to find Prime Factors?

Ok , I have an Fx-991ES CASIO **calculator**, I’m writing math tomorrow and I need to know how to find the prime factors , like 6 is 3 x 2 , I need to be able to do this with large numbers on a **calculator**

### admin answers:

Unfortunately you can’t with that calculator.

Unlike the 83GT Plus and 85GT Plus, the 991ES Plus doesn’t have a factorisation function (see the specifications http://www.casio.co.uk/products/calculators/scientific-calculators//Product/FX-991ESPLUS-SA-UH/ ).

They probably won’t throw vast numbers at you, and it can be done by hand: you progressively divide by visible factors. Divisibility tests are:

2 … Number is even

3 … Sum of digits divides by 3

5 … Number ends with 0 or 5

9 … Sum of digits divides by 9

10 … Number ends with 0

11 … Sum of odd and even digits is equal

Lisa asks…

## Why does the calculator only calculate multiples of .5 factorial, and why does it not calculate negatives?

Since the Gamma function can approximate these answers.

### admin answers:

That’s because calculators are probably using a special case of the gamma function to evaluate

(n + 1/2)! = sqrt(Pi)*[Product of all odd positive integers till 2n+1]/2^(n+1)

e.g. 3.5! = sqrt(Pi)*1*3*5*7/2^4 = 11.63

I am surprised that your calculator can actually do this – mine cannot!

The gamma function is not defined for negative integers – it diverges – see plot below

Maria asks…

## How do i make answers appear with commas on my ti-83 calculator?

For example, right now solutions appear as 3200 and i want them to instead appear as 3,200. often the solutions to my calculations are really high numbers and its easy to read them wrong when the answers are not in a form with commas in them.

### admin answers:

The TI-83 (Plus) calculators don’t support that natively, unfortunately. Perhaps a program exists out there that supports this feature, but I’ve not seen any.

Certain HP calculators support that feature, but for whatever odd reason, Texas Instruments didn’t include it.

Mary asks…

## When is my highest chance of being pregnant?

I just had a late period. I had one 12/15 and then it was late but came yesterday 1/30. That’s forty **odd** days. The one between November and December was 41 days also.

So… If I’m on my period now, when will I ovulate and what’s the best time to have sex to increase chances. Also any tips would be great too

### admin answers:

The time most women are most fertile is from 11-18 days after her period (sperm can live in a woman for 3-5 days,and if she releases an egg late,that’s why the time after) but on average it’s 14 days AFTER THE FIRST DAY of her last period. Also look at sites like http://www.babycenter.com,and stuff like that where you’d be able to find an ovulation calculator.

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