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Math Sl paper 1 2015


Mohammad

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did anyone get the area of the triangle Q on the vector part on P1? I got some complex number involving roots so that doesn't seem right for a P1 ... 

whoa...did you get something to do with root 66 by any chance? I thought it was the WEIRDEST thing... But I'm pretty sure I got it wrong :(

 

root 66 was somewhere in my answer .. it was a fraction i think .. that Q was going so well until they asked us to find that area .. 

 

I know right? WHOA, so I might get partial marks? That's good enough for me right now, something's better than nothing. Especially because there's quite a high possibility I lost 13 marks in the last 2 letters of #10 :( That stupid stupid question. I hate Ann, she should lose the game (no offense intended to any Ann's out there)

 

when are we allowed to discuss paper 2 .. it was absolutely terrible

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did anyone get the area of the triangle Q on the vector part on P1? I got some complex number involving roots so that doesn't seem right for a P1 ... 

whoa...did you get something to do with root 66 by any chance? I thought it was the WEIRDEST thing... But I'm pretty sure I got it wrong :(

 

root 66 was somewhere in my answer .. it was a fraction i think .. that Q was going so well until they asked us to find that area .. 

 

I know right? WHOA, so I might get partial marks? That's good enough for me right now, something's better than nothing. Especially because there's quite a high possibility I lost 13 marks in the last 2 letters of #10 :( That stupid stupid question. I hate Ann, she should lose the game (no offense intended to any Ann's out there)

 

when are we allowed to discuss paper 2 .. it was absolutely terrible

 

Oh no! Really? :( I made a stupid mistake in Paper 2 which I'm beating myself up over...well I don't know what time it is for you. It's 10 PM for me and we can discuss it at 8:30 AM tomorrow. 24 hours after the exam

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I did TZ1. Personally, I feel the grade boundaries this year should be lower. Can't tell if its my personal bias or desperation though lol.

I know the feeling mate. I felt like they should be lower too...just in comparison to the past papers. But I can't tell if it's just because of my biased perception of how much harder this exam felt rather than if it actually was.

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I did TZ1. Personally, I feel the grade boundaries this year should be lower. Can't tell if its my personal bias or desperation though lol.

I know the feeling mate. I felt like they should be lower too...just in comparison to the past papers. But I can't tell if it's just because of my biased perception of how much harder this exam felt rather than if it actually was.

 

I found P1 to be pretty straightforward, with the exception to the last probability Q involving Ann. P2 wasn't nearly as fun though :( 

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I did TZ1. Personally, I feel the grade boundaries this year should be lower. Can't tell if its my personal bias or desperation though lol.

I know the feeling mate. I felt like they should be lower too...just in comparison to the past papers. But I can't tell if it's just because of my biased perception of how much harder this exam felt rather than if it actually was.

 

I found P1 to be pretty straightforward, with the exception to the last probability Q involving Ann. P2 wasn't nearly as fun though :(

 

How do you guys feel about P1?

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Does anyone remember the answer for #7 TZ2? (the fair game question) :D

I got 25 dollararrow-10x10.png. :o What about you?

I thought it was pretty hard exam...specially the last question. Whole question 10 was horrible... :(

I got the same answer, hope its correct.. :3

Actually it's not . You can never win your money back and the additional profit in a betting game ( which it was) . I opened a betting calculator after the exam , the answer was plain 15

 

Was it really? That's what I got, but listening to people after the exam all get 25 I figured it was plain wrong. 25 makes perfect sense as I redo the problem. 

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Does anyone remember the answer for #7 TZ2? (the fair game question) :D

I got 25 dollararrow-10x10.png. :o What about you?

I thought it was pretty hard exam...specially the last question. Whole question 10 was horrible... :(

I got the same answer, hope its correct.. :3

Actually it's not . You can never win your money back and the additional profit in a betting game ( which it was) . I opened a betting calculator after the exam , the answer was plain 15

 

Was it really? That's what I got, but listening to people after the exam all get 25 I figured it was plain wrong. 25 makes perfect sense as I redo the problem. 

 

15 is wrong. Think about it. Their logic is that if you play 6/10 games, you will lose 60$, and when you play the remaining 4 games you will gain 60$, which means you win as much as you lose. However, they forget that the fee to play is 10$. So in the end in 10 rounds you will pay 100$, win 60$, hence lose 40$, and showing that when k=15, the game is not fair.

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Does anyone remember the answer for #7 TZ2? (the fair game question) :D

I got 25 dollararrow-10x10.png. :o What about you?

I thought it was pretty hard exam...specially the last question. Whole question 10 was horrible... :(

I got the same answer, hope its correct.. :3
Actually it's not . You can never win your money back and the additional profit in a betting game ( which it was) . I opened a betting calculator after the exam , the answer was plain 15

Was it really? That's what I got, but listening to people after the exam all get 25 I figured it was plain wrong. 25 makes perfect sense as I redo the problem.

15 is wrong. Think about it. Their logic is that if you play 6/10 games, you will lose 60$, and when you play the remaining 4 games you will gain 60$, which means you win as much as you lose. However, they forget that the fee to play is 10$. So in the end in 10 rounds you will pay 100$, win 60$, hence lose 40$, and showing that when k=15, the game is not fair.

I also got 15 and it still makes more sense to me than anything else. Does anyone remember how many marks the question was worth?

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Does anyone remember the answer for #7 TZ2? (the fair game question) :D

I got 25 dollararrow-10x10.png. :o What about you?

I thought it was pretty hard exam...specially the last question. Whole question 10 was horrible... :(

I got the same answer, hope its correct.. :3
Actually it's not . You can never win your money back and the additional profit in a betting game ( which it was) . I opened a betting calculator after the exam , the answer was plain 15
Was it really? That's what I got, but listening to people after the exam all get 25 I figured it was plain wrong. 25 makes perfect sense as I redo the problem.
15 is wrong. Think about it. Their logic is that if you play 6/10 games, you will lose 60$, and when you play the remaining 4 games you will gain 60$, which means you win as much as you lose. However, they forget that the fee to play is 10$. So in the end in 10 rounds you will pay 100$, win 60$, hence lose 40$, and showing that when k=15, the game is not fair.

I also got 15 and it still makes more sense to me than anything else. Does anyone remember how many marks the question was worth?

 

Could you explain how exactly?

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I did it like E(X) = 10$.

And by assuming that I got 25$, but apparently you were supposed to subtract 10$ from it and get 15$.

But why would you subtract 10? I mean, the goal is to have a fair game, meaning that the net gain is 0. Hence, if you pay 10 and have an expected value of 10, problem solved...

Edited by dorianb
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I did it like E(X) = 10$.

And by assuming that I got 25$, but apparently you were supposed to subtract 10$ from it and get 15$.

But why would you subtract 10? I mean, the goal is to have a fair game, meaning that the net gain is 0. Hence, if you pay 10 and have an expected value of 10, problem solved...

 

I don't understand why you'd subtract either, but this is my friend told me. She did it the same way I did but apparently it's wrong.

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I did it like E(X) = 10$.

And by assuming that I got 25$, but apparently you were supposed to subtract 10$ from it and get 15$.

But why would you subtract 10? I mean, the goal is to have a fair game, meaning that the net gain is 0. Hence, if you pay 10 and have an expected value of 10, problem solved...

 

I don't understand why you'd subtract either, but this is my friend told me. She did it the same way I did but apparently it's wrong.

And how do you know it is wrong?

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I did it like E(X) = 10$.

And by assuming that I got 25$, but apparently you were supposed to subtract 10$ from it and get 15$.

But why would you subtract 10? I mean, the goal is to have a fair game, meaning that the net gain is 0. Hence, if you pay 10 and have an expected value of 10, problem solved...

 

I don't understand why you'd subtract either, but this is my friend told me. She did it the same way I did but apparently it's wrong.

And how do you know it is wrong?

 

 

Okay I got 15, and during the exam my reasoning went like this. 

 

White: P(0.6) = she wins nothing (yet I reasoned that she already looses $10 by even playing the game, thus her NET gain/loss is -10, after all in order for it to be a "fair game" it's the net profit that must equal to zero, or so I thought)

Black: P(0.4) = she wins K.

 

Thus my E(X) was:

 

0.6(-10) + 0.4(k) = 0

-6 = 0.4k

 

15 = k

After the exam though, I listened to someone explain why they got 25 and I suppose that also made sense.

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8? I thought it was worth 7...the one about Ann, right? I didn't realize it was geometric. I was so stuck on trying to figure out which probability concept to use that I didn't consider it was from another unit :(

I knew it was geometric when it told us to find k and r in (3/8)r^k, which takes on the form of a geometric sequence. I still got it wrong though. What did people put for k and r?

 

I remember k was 9, and r was the probabilities of them both losing multiplied by each other.

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8? I thought it was worth 7...the one about Ann, right? I didn't realize it was geometric. I was so stuck on trying to figure out which probability concept to use that I didn't consider it was from another unit :(

I knew it was geometric when it told us to find k and r in (3/8)r^k, which takes on the form of a geometric sequence. I still got it wrong though. What did people put for k and r?

 

I remember k was 9, and r was the probabilities of them both losing multiplied by each other.

 

Oh damn. I thought it was just the probability of HER losing...but I guess I got k right so I'll get something for that?

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