extension 1 maths

I need help with the following: 1) A student writes a random three-digit number using the digits 1-9. what is the probability that the three digits in the number are all the same? 2) five cards are drawn from a standard pack of 52 playing cards (without replacement). what is the probability of...

Math Advanced + Extension 1 Combined Notes (185 Pages, 2U HSC Mark 99/100, 3U HSC Mark 48/50) Includes full worked answers for all features questions, clearly set out notes. See sample in attachment, if you would like to see more please contact me. Topics include: Curve Transformations...

So I was doing some 2020 school trial papers and I found that none have included sqrt(p(1-p)/(n-1)) as the answer for sample standard deviation. Just wondering what do you guys think, would n-1 be safer in HSC or n will be fine?

The angle between two vectors u=i-3j and v=ai+5j is 120°. Find a correct to 1 decimal place. I've tried substituting into the scalar equation but I can't get the answer

So I was bored and I decided to do the HSC 3U Maths for 2019. Please tell me if any of the answers are wrong. I am not a HSC student lol. In my opinion the exam was harder than last year so hopefully it scales better. Other than that have a look a through it