Post me your hardest maths question you know

dowie · 15 Feb 2011 at 23:00

w3bbo said:
I'm totally lost on the above

3x9 = 27 (+2 the waiter kept as a tip)= 29

So where did the other pound go?

They paid £27 in total for the meal that should have been £25 because the waiter took an additional £2 as a tip.

They got £3 back

There is no missing pound - the £27 paid can be broken down into the £25 for the meal and the £2 for the waiter.

Fenris · 15 Feb 2011 at 23:02

w3bbo said:
No.

The three men in effect pay £9 each (as they all got a £1 refund on the £10 each they paid) therefore the 3 men paid £9 each for the meal = £27 yes?

No.

Clearly you know the answer to this, anyone with half a braincell does.

The men do not pay £9 each, the meal is £25 which you can't divide by 3, that is what screws up peoples thought process.

For anyone who has trouble with the question, think of it in terms of where the £30 they give to the waiter goes.

£25 - Till
£3 - Men
£2 - Waiters Pocket

There is no £9.

dowie · 15 Feb 2011 at 23:03

Kenai said:
He needs a speed of 90mph to average 60mph over the two laps,

nope

Cybermyk · 15 Feb 2011 at 23:04

Kenai said:
You've phrased that slightly wrong I think.

He needs a speed of 90mph to average 60mph over the two laps, however, doing so would not allow him to qualify for the race.

What I think you intended to ask was: A racing driver had to have an average speed of 60mph across two laps in order to qualify for a race - he had engine trouble on the first lap so only managed and average of 30mph - how fast does he have to travel on the second lap in order to qualify for the race?

If he needed to average 60mph for two laps and only managed one at 30mph then shirley he is out of time?

Kenai · 15 Feb 2011 at 23:05

dowie said:
nope

Yes, he does.

The 'clever' part of that problem comes from the fact that having completed one lap at 30mph he will have taken as long as he would have needed to have completed both laps in, ergo the second lap is irrelevant as he's already hit the time limit after one lap.

However what you actually asked was just what speed would he need to average 60mph, which would be 90mph, hence my comment that I think you phrased your question wrong and didn't actually ask what I think you intended to ask.

All you asked was what speed would he need to do on the second lap to average 60mph over both, the answer to which is 90mph. Had you asked 'to qualify' then obviously, there is no answer as he is already out of time and cannot qualify.

SpeedFreak · 15 Feb 2011 at 23:09

Kenai said:
Yes, he does.

The 'clever' part of that problem comes from the fact that having completed one lap at 30mph he will have taken as long as he would have needed to have completed both laps in, ergo the second lap is irrelevant as he's already hit the time limit after one lap.

However what you actually asked was just what speed would he need to average 60mph, which would be 90mph, hence my comment that I think you phrased your question wrong and didn't actually ask what I think you intended to ask.

All you asked was what speed would he need to do on the second lap to average 60mph over both, the answer to which is 90mph. Had you asked 'to qualify' then obviously, there is no answer as he is already out of time and cannot qualify.

I was actually thinking of this one, hence the answer of infinitely lol. The answer to the America one is 33.3 in hindsight

dowie · 15 Feb 2011 at 23:09

Cybermyk said:
If he needed to average 60mph for two laps and only managed one at 30mph then shirley he is out of time?

yep

same answer as the spacecraft question posted earlier

- tis a silly question - lots of people will incorrectly answer 90mph somehow thinking that doing one lap at 30 and one lap at 90 will average out to be 60mph across both - doing 1 lap at 30mph then a second lap at 90mph gives an average speed of 45 mph across both laps

dowie · 15 Feb 2011 at 23:11

Kenai said:
All you asked was what speed would he need to do on the second lap to average 60mph over both, the answer to which is 90mph. Had you asked 'to qualify' then obviously, there is no answer as he is already out of time and cannot qualify.

sorry you're confused - qualifying and averaging 60mph over both are the same thing - in order to qualify he needs to average 60mph over both

doing 1 lap at 30mph and another at 90mph gives an average of 45mph over both laps

[FnG]magnolia · 15 Feb 2011 at 23:13

dmpoole said:
If you cut a sandwich in half is it now 2 sandwiches?

That was the best thread

Parky · 15 Feb 2011 at 23:16

What is the air-speed velocity of an unladen swallow?

Kenai · 15 Feb 2011 at 23:16

You're right about the 90mph figure being wrong, that's my maths skills going down the pan as I get more tired, but the way you phrased your question, qualifying and averaging 60mph aren't necessarily the same thing, they could be considered separately and it would be possible to average 60mph and not qualify... just not at a 90mph second lap

iamTakeo · 15 Feb 2011 at 23:18

How long is a piece of string?

Cybermyk · 15 Feb 2011 at 23:18

Parky said:
What is the air-speed velocity of an unladen swallow?

African or European?

Kenai · 15 Feb 2011 at 23:20

Kenai said:
You're right about the 90mph figure being wrong, that's my maths skills going down the pan as I get more tired, but the way you phrased your question, qualifying and averaging 60mph aren't necessarily the same thing, they could be considered separately and it would be possible to average 60mph and not qualify... just not at a 90mph second lap

Actually, i've confused myself now, I don't even know what I think, i'm going to bed

edit - In fact I do know but I was totally wrong and I now feel ashamed and stupid for even trying to argue that one. I'm still going to bed

Cosimo · 15 Feb 2011 at 23:23

Parky said:
What is the air-speed velocity of an unladen swallow?

dowie · 15 Feb 2011 at 23:24

Kenai said:
You're right about the 90mph figure being wrong, that's my maths skills going down the pan as I get more tired, but the way you phrased your question, qualifying and averaging 60mph aren't necessarily the same thing, they could be considered separately and it would be possible to average 60mph and not qualify... just not at a 90mph second lap

Sorry, don't mean to be pedantic but I defined qualifying, at the start of the question, as being averaging 60mph over both laps.

A racing driver had to have an average speed of 60mph across two laps in order to qualify for a race

edit - no worries just saw your other post - the question is designed to confuse I guess so reading it when tired is likely going to cause confusion.

Kenai · 15 Feb 2011 at 23:25

LOOK, I've admitted I was wrong, just leave me alone

Redmint · 15 Feb 2011 at 23:30

SpeedFreak said:
I was actually thinking of this one, hence the answer of infinitely lol. The answer to the America one is 33.3 in hindsight

Grr, your 'faster' comment on the first page of this thread actually had me confused for a while.

dowie · 15 Feb 2011 at 23:37

Kenai said:
LOOK, I've admitted I was wrong, just leave me alone

Sorry dude

I mis-read the spaceship one and got that wrong too tbh...

33.3r mph is the answer as has been posted

though the guy writing the question got it the wrong way around and seemingly intended to have essentially the same question as the racing driver one

Shayper · 15 Feb 2011 at 23:53

Okay, this one is a mind****

3 friends go to a restaurant.

They spend a total of 25 pounds, but only have 10 pounds each on them. They pay the waitress, who, being a crafty one, takes 2 pounds in tips. so she gives each of them one pound as change.

Therefore they each spend 9 pounds, as 10-1 = 9.

However (9x3) -[the amount they each spent]- +2 -[the amount the waitress took in tips]- = 29.

So, where did that last pound go?

Mhm