blonde poker forum

Having not studied Maths for well over 20 years my 12 year old lad asked me for some help with his homework.

The question is:

Jen is y years old and her mother is 27 years older. Together their ages total 45 years.
a. In terms of Jen's age, how old is her mother now?
b. Form an equation in y and solve it to find Jen's age and her mother's age now.

He knows the ages are 9 and 36 but is struggling with forming the equation and Im just brain dead today.

Any help appreciated.

a) y + 27

b) y + (y+ 27) = 45
    2y = 18
      y = 9

And the mother is 36 based on a)

Tyvm

One more please.

Question:
Sonia is n years old now and Cynthia, her sister, is 2 years older. In 5 years time the sum of their ages will be 20.
How old is Sonia now?
How old will Cynthia be in 5 years time?

Again he knows the answers but not the equations to get to the answers.

Thanks

In 5 years time:

n + (n+2) = 20
2n + 2 = 20
2n = 18
n = 9 (Sonia)

Cynthia = 11 (n + 2)

Now:

5 years earlier so Sonia is 4.

Thanks again

sigh - was going to do some teaching but CF was too quick with just the answer

Feel free to eloborate

Knowing the answer means it doesn't really work after the fact

But basically the formula is just constructed from the words. Take the words like age (n),her sister is two years older (so n+2) - you then build up the rest of the formula following the words so that = 20, then you take off 5 because that's in 5 years time.

Like I suggested, it seems a bit obvious just spelling it out like that once you've seen the answer - people can kind of remember stuff by it being explained, but you really learn by working it out yourself.

This is fantastic.... Celticalike has got u to do his lads homework and he looks like a genius in his child's eyes... Nice moves bobo

Has this one been done on here before?

I have a standard coin. But... it is biased to one side. We don't know which side, nor do we know the size of the bias. How can we use this coin to get a genuine 50/50 chance?

I totally agree with your sentiments on learning. I just couldnt elaborate on it for my lad.
Unbelievably I was kid genius at Maths and was put up for A level at 13. I just have not done anything significant in numbers since I was 18, 26 years ago. I used to love numbers and recently bought a book called 'Alex's adventures in number land' excellent read if anyone's interested.

Lol, lad sitting next to me and knows his dads a fraud.

Do the thing where you hide it in one hand and get someone else to guess which hand it is in.

Nope. Too many other factors for that to be 50/50.

like what?

one suspects you could take a Chernoff bound to determine which side is biased and then take a decent sample based on that bias....although I'm probably overegging it for a random question on a poker forum? :D

write a number on it using a pen, maybe a green one. then ask someone to guess whether it's an odd or an even number. they'll probs get it right about 50% of the time

the date on the coin could be odd or even, so you wouldn't need to spend the coin to buy a green pen

confirmed overegged it. sigh.

I figured the date thing would be biased to the last full year as there'd be more in circulation

Rather than flip the coin just take it out of your pocket and place it on a table.

Assuming you don't know which way the bias works I'm pretty sure that'd be 50/50.

Or we could just flip it and call heads or tails. As we don't know what way it's biased it's still 50/50 whether we get it right or not

Take the coin and throw it at cf's head. You'll either hit him or you won't - 50/50.

nah - what if the coin is 100% biased?

Even if it's double headed/tailed we're still 50/50 to get it right if we don't know which one. Ignorance ftw

ok, say 90% it's heads and 10% it's tails.

we pick heads 50% and tails 50% over 100 trials (assume no variance and that 100 is a big enough number to make results match expectation perfectly)

when we pick tails, we're never right 50% of the time....

agreed but I'm only talking about a one off single flip

question asked 'How can we use this coin to get a genuine 50/50 chance?' and that's what we'd get once

Nope. You're making an assumption that neither person knows about the bias, and this might not always be the case.

The correct answer will always work, no matter the bias (as long as it's not doublesided/100% of course).

So that was the royal we and not a co-operative effort from a pair of tossers?

Use the coin to buy another one, or a dice, or a deck of cards.

no I'm not, you told us that



my answer is correct unless you want to move the goalposts

Is also correct.

When CF says:


What he actually means is:

This method only works if the person doing the hand holding is 100% unreadable.

My solution can be mathematically proven. It's done by tossing the coin and observing the result. (hint: results). No trickery etc required.

you could just accept that there's more than one way to answer the question the way you worded it

Ask punter to call heads or tails (lets say he calls tails)

Toss coin twice.  If it is a tails and then a tails then start again.
If it is a heads and then a heads then start again
If it is a heads and then a tails he loses
If it is a tails and then a heads he wins

The answer works for whatever bias the coin has, but lets assume it is 10% heads and 90% tails. 

Chances of HT = 9%
Chances of TH = 9%

By removing all other possibilities we have a total "chance population" of 18% and we now have a 50/50 proposition.

When the guy calls the toss Tails he is in effect picking the Tails/Heads combo without knowing it and the other guy has the Heads/Tails combo.

Ah - it pulled the old Ten of Hearts when I typed TH.

"Chances of Heads/Tails = 9%
Chances of Tails/Heads = 9%"

in b4 cf gives a reason why this is wrong

I think it's mathematically sound, but I'm not sure if I am allowed to "kick out" toss observations like I have suggested.

good work. this is kinda like taking the C boundary but without all the expensive maths ;)

That is indeed the answer :)

worst thread ever

this

just cos you didn't get the right answer ;)

FYP

This answer is based on a condition that isn't specified in the original question: What happens if the bias is 100%? The answer is only correct for bias < 100%. Very poorly worded question, so I agree with gatso.

Still works for 100% bias.  Both players have a 0% chance and the flips last forever, but theoretically both people still have the same chance of winning so it is "fair".

It's not a genuine 50/50 chance if it's 100% biased. You can't multiply 0 by anything to get to 50. 0/0 is indeterminate. My point stands :P.

Edit: To clarify my point - if the question had said, "the same chance of winning", I would accept your response. But it doesn't. 50/50 ≠ 0/0.

Point conceded.

Thanks, but are you sure you're on the right forum? This is blonde. People don't just concede points. I want an ARGUMENT, FFS

:D

it's alright, cf will be along in a bit to attach some random caveat that wasn't included in the original question