Maths S1 HELP NEEDED - URGENT

[SarcasticNerd]

Hi. I'm prolly screwed in Maths S1 paper tomorrow. However, people please help me out a little.

When do you use nPr and nCr formula? I always mix them up so if somebody could please help me with that. And if somebody have any last minute revision notes of S1 for me, I'll really appreciate it. And any other tips related to S1 will be highly appreciated. Thanks.

 

[n.r.s.007]

nCr is used when you want to find out the number of different selections where the order does not matter. (Random selection)
nPr is used when you want to find out the number of different arrangements where the order is definitely considered.
if you multiply nCr with r!, you get nPr
I have attached a compilation of s1
Revise binomial to normal distribution; it always comes for 5 marks (10% of the paper)
Learn how to compare box plots and the advantages and disadvantages of all types of representation of data
Best of luck

 

[Zash Riyash]

As far as S1 is concerned you must stay cool as a cucumber, for the paper. Because statistics paper is more of logic(quite often). So stay cool, and do well!

 

[SarcasticNerd]

THANK YOU! YOU AWESOME PEOPLE OF EARTH! Now, one more thing. I have seen some questions in past papers where they divide, like it would be something 5C2 x 5C3 / 4C2 x 4C1.

So my question is why do they divide? Like whats the logic behind it?

 

[n.r.s.007]

That's when they are finding the probability of an event happening.
Suppose a question asks to find the probability of 1 girl and 2 boys being chosen to play as a team out of 6 girls and 3 boys.
So, you multiply 6C1 with 3C2 to find the number of ways this can happen. This is divided with total number of ways of choosing a team, regardless of gender.
So it is 6C1 x 3C2 / 9C3