SC mathematics Marathon (1 Viewer)

RealiseNothing

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15 balls with the numbers 1 to 15 written on them are placed into a box. What is the possibility of pulling out a prime number?
That was in my School Trials lol, I'm guessing you did the same one as me.
 

zombies

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Lol, what?
Isn't it 7/15?
Prime numbers: 1, 2, 3, 5, 7, 11, 13
Therefore: 7 possible prime numbers
Total possible numbers: 1, 2, 3, …, 15 = 15
therefore probability = 7/15
haha silly! I got that question wrong as well. 1 isn't actually a prime number.. I was pretty annoyed afterwards when I found out lol.
 

RealiseNothing

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haha ooh~ what mark did you get?
97, read a question wrong and lost 3 marks :(, should of had 100

@1 not being a prime

They don't consider 1 to be a prime anymore because it means that there are infinite prime products of any non-prime integer.

For example: 10 can be written as 5 times 2, so it has 1 product of just primes. But if 1 were a prime, then we could say 5 times 2, 5 times 2 times 1, 5 times 2 times 1 times 1, and so on, meaning it would be infinite.
 

Some Vunt

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haha silly! I got that question wrong as well. 1 isn't actually a prime number.. I was pretty annoyed afterwards when I found out lol.
Hahah. No wonder I failed MX2 last week.
I got 96 on the SC though. Which I think was the highest or second highest at school and I didn't study and I came ~20th in the in school assessments. So, SC is pretty easy, don't stress.

Btw, I thought the definition of a prime number was a number that only had a factor of 1 times itself. And 1 has factors 1x1.

Do you guys know what we have to get in order to get a band 6?
No idea.
 

bleakarcher

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no actually, that would have stunned many people with less exposure to these questions as some dont trust their ability in algebra
 

zombies

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97, read a question wrong and lost 3 marks :(, should of had 100

@1 not being a prime

They don't consider 1 to be a prime anymore because it means that there are infinite prime products of any non-prime integer.

For example: 10 can be written as 5 times 2, so it has 1 product of just primes. But if 1 were a prime, then we could say 5 times 2, 5 times 2 times 1, 5 times 2 times 1 times 1, and so on, meaning it would be infinite.
Aw you beat me by one! Grr. I stuffed up two multiple choices cos I was stupid and misread them, and then I got the prime number question wrong and in question where you had to draw a square pyramid I forgot to indicate that the base was actually a square and I didn't draw on any right angles or the dashes to show that the sides were all equal.. haha

Btw, I thought the definition of a prime number was a number that only had a factor of 1 times itself. And 1 has factors 1x1.
Well yeah and then so 1 only has 1 factor, like 1 and itself would be 1 and 1, so then it doesnt really have two factors? if that makes sense.. kinda makes sense in my head lol.
 
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