Question

Probablity question

Answer 1

que:

On her vacations Veena visits four cities (A, B, C and D) in a random
order. What is the probability that she visits
(i) A before B? (ii) A before B and B before C?
(iii) A first and B last? (iv) A either first or second?
(v) A just before B?

Answer 2

probably not

Answer 3

The number of ways by which veena can visit is 4!=24

Answer 4

yes

Answer 5

i can'r go further

Answer 6

*can't

Answer 7

i guess you can list ways in which a comes before B and count them A bit tedious though

Answer 8

yes that is tediuos i want another time saving way

Answer 9

or
if A is the first then how many ways can the others be visited
3*2 = 6
if A is 2nd and B 3rd or 4th - thats 2 ways

Answer 10

- no the last one is 4 ways

then we have A 3rd and B 4th - 2 ways

total 6 + 4 + 2 = 12

so first one is 12/24 = 1/2

Answer 11

to be honest I hate probability!

Answer 12

sumilarly B before C = 12 ways ?

Answer 13

yes must be

Answer 14

can we multiply these now to get the compound probability?

Answer 15

ok i need to find now the common between A before B and B before C

Answer 16

the question is are they independent events?

Answer 17

i don't understand how independent events means here

Answer 18

there are 12 events in both A before B and B before C and i need to find the common events between them

Answer 19

(A before B) \(\Large \cap\) (B before C)

Answer 20

by listing and counting there are 4 of them

Answer 21

ok so i need to list them necessrily

Answer 22

i'm afraid i dont remember all the set theory applied to probability

Answer 23

ok so same for 3, 4 and 5 , listing ?

Answer 24

questions iii to v are quite straightforward - i think!!

Answer 25

for q iii it is the number ow ways you can arrange the 3 letters between A and B

Answer 26

= 6 right?

Answer 27

3!=6 , yes

Answer 28

for iv

A first = 3! ways
+ 31 ways with A second

Answer 29

* 3!

Answer 30

ok

Answer 31

v

AB to begin - - 2 ways
AB 2nd and 3rd - 2 waya
AB last - 2 ways

Answer 32

nice question

Answer 33

yea it is

Answer 34

AB--
A_B__
A__B
_AB__
_A_B_
_A__B
__AB

i calculate 7 ways for v.)

Answer 35

@welshfella

Answer 36

just another way of thinking about it"!