A-Level Maths: M1-15 [Probability: Two-Way Table Example 2]

[NM-ytfs]

The wording in this question could be a bit more clear as it could also be interpreted as 6% of the students on route A are left handed and 8% of the students on route B are left handed rather than 6% and 8% of the total students. Always tricky with stats questions!

[fardinahmed]

Hi, when u did 0.34^3, i was confused as why does the probability not change after selecting the first person? Because that person cant be selected again.

[short-shots]

For part b, is there any quicker way to get how many ways through there could be in the exam? I am asking because last time you should a way to do which was to factorial the number of people selected, but this one was a bit different and it would save time in the exam if there was a quicker way to find how many roots there could be

[hb]

Hi, when I'm faced with a probability problem, how do I know when to use a two-way table and when to use tree diagrams? What's the indicators in the question for the different methods?

[veem]

Hi JB; just wanted to say your videos are really, really inspirational; thanks for all the effort dedication you have put in / are putting in to create a quality set of videos. FYI I've gone through about 400 of your videos now and this is the first time I've hit a snag.


I do have a "daft lad" comment to make on this particular problem; so hopefully you'll keep me honest on this :-). Like N M (from 6 months ago) I found the wording contained some ambiguity - but for a different reason (hence more than happy for you to get me back on side). I tried figuring this out before looking at your run through and had trouble comprehending the third sentence. I was content enough with the "6% and 8% respectively" left handed people in sentence two; however, the "60% opt for Route B" I really struggled with. 60% of what? 60% of all students? Given it is a new sentence (there is a full stop after the word "respectively" right?) I did not want to assume you were referring to just the left handed students. So, should the problem have called this out unambiguously i.e. 60% of the left handed students opt for Route B?


Like I say, apologies for the daft lad question, and thanks once again.

[chewypiano]

for the 0.34 ^3 bit would that not imply that the same student could be picked again? should it not be 0.34 X (0.34-x) X (0.34-2x) ???? eg lets say 100 people( 34 x 33 x32 )/ (100 x 99x98)??? or is this probability based upon assumption that any difference between 0.34^3 probability and the exact probability is negligible???

[itsjennelle]

How do u know when you need to use a two way table or tree diagram etc

[ananyaryali]

Thank you very much for your videos- they have been so useful. How do you know when to use factorial when calculating number of options and how does using 3C2 work with finding number of options? Thanks

[engineeringmadeasy]

And in the exam how do I understand if there are 3 ways without drawing that complicate Tree Diagram?

[VirlTks]

hi, how will you know wether to use the two way table or a tree diagram for these questions

[genaromarzotta]

Hello, when you times by 3 I thought you had to multiply by 3 factorial, is this not right?

[haisamnadeem]

hi, how will the ncr formula work for the part c i cant figure it out to find possible combinations

[harrysmith]

Is there a faster way to work out how many different orders there could be without drawing out the probability tree?