Question

A four digit number (with no repetitions) is to be formed from the set of numbers {0,1,2,3,4,5,6,7}. Find the probability that the number
a) is less than 4000
b) is less than 4000, given that it is greater than 3000

Answer 1

i have the answer to part b only

numbers greater than 3000 can start with 3, 4, 5, 6 or 7
numbers from the above sample space less than 4000 have to start with 3
reqd. probability
= 1/5
= .2

and here is my source '
http://au.answers.yahoo.com/question/index?qid=20100403031552AAYdtuw

Answer 2

for the first part @JayDS

Answer 3

there are 8 numbers form 0-7 but we have only four places without repetetions

Answer 4

so if for the first place there are 8 choices
for the second place there are 7 choices
for the third place there are 6 choices
for the forth place there are 5 choices

Answer 5

so to get the total options u multiply 8x7x6x5

Answer 6

yep kk.

Answer 7

but probability so it would be over the total

Answer 8

so 8x7x6x5/8! right?

Answer 9

then to find the probability of numbers less than 4000
u look at the numbers that can be formed that are less than 4000 which will be mostly 3765 and under

Answer 10

meaning that we are going to be using numbers 3,2,1,0 for the first place
and there will be 7 numbers left for the second place and 6 for the third and 5 for the forth

Answer 11

so it will be 4x7x6x5/ 8x7x6x5

Answer 12

@JayDS by the way the answer that is for part b is wrong

Answer 13

it is supposed to be the follwoing

Answer 14

if the numbers have to be bigger than 3000 and less than 4000

then for the first place there is only one number right which is 3

Answer 15

for the second is 7
for the third is 6
and for the forth is 5

Answer 16

so the answer for part b would be

1x7x6x5 / 8x7x6x5

Answer 17

@JayDS

Answer 18

but the answer in my textbook says 0.2

Answer 19

for part b.

Answer 20

ohh ok then what does it say for part a

Answer 21

3/7=0.429

Answer 22

oh ok then sorry all my answers are wrong :(