Probability question

This is some help for q1 on page 254.

(a) Use the same approach as we used today for "roll a die - what is the probability of getting a 4?" type of question. There are 6 sides, one of them is a 4 so the probability P(4) = 1/6.
If you were asked for the probability of getting a 4 or a 3, then it would be P(4or3)= 2/6 = 1/3

(b) Arrangements. There are 6 letters, so there are 6 options for the first position, 5 for the second and so on.
If the first position must contain B, then there is 1 option for that position, 5 for the second and so on.
For the third part of this question, there are further restrictions. Start with the most restricted positions and then work out how many options remain for the other positions.

(c) Similar to the arrangements questions, but with a bit of extra logic required.
For part (iii) remember that there are only 4 digit positions to be filled, so there are 6 options for the first position, 5 for the next, 4 for the next and 3 for the last.
For part (iv) if the number is to be >4000 then the first digit must be either 4 or 5 - in other words there are only 2 options.

We won't get much more of a chance to revise probability so look over the whole chapter 11 now.