A Four digit safe code does not contain the digits 1 and 4 at all. What is the probability that it has at least one even digit?
I don't have an OA.
P(atleast one digit is even) = 1 - P(all digit odds)
We have 4 odd digits excluding 1 (3,5,7,9).
So, possible 4 digit odd numbers = 4*4*4*4
All possible 4 digit numbers = 7*8*8*8 (Ensure that 1st digit is not 0 and exclude 1 and 4)
P(all digits odd) = 4*4*4*4/7*8*8*8 = 1/14
P(atleast one digit is even) = 1 - 1/14 = 13/14
Any different solution for this . I am very bad at probability
Probability
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 70
- Joined: Sun Mar 18, 2007 9:35 am
- Location: mumbai
- Followed by:1 members
4 digit safe code without 1 and 4
possible digits for each digit 0,2,3,5,6,7,8,9 ie 8 ways
total 8*8*8*8
consider all odd digits so possible digits 3,5,7,9 ie 4 ways
total 4*4*4*4
So atleast one even is= 8*8*8*8 -4*4*4*4 / 8*8*8*8
= 1 - 1/16 = 15/16
Why should the first digit not be zero????????????
possible digits for each digit 0,2,3,5,6,7,8,9 ie 8 ways
total 8*8*8*8
consider all odd digits so possible digits 3,5,7,9 ie 4 ways
total 4*4*4*4
So atleast one even is= 8*8*8*8 -4*4*4*4 / 8*8*8*8
= 1 - 1/16 = 15/16
Why should the first digit not be zero????????????
If It Is To Be It Is Up To Me
- gabriel
- Legendary Member
- Posts: 986
- Joined: Wed Dec 20, 2006 11:07 am
- Location: India
- Thanked: 51 times
- Followed by:1 members
... i agree with RAGS ... 0 can be the first number .. wen u say that 0 as the first number wuld reduce it to a 3 digit number .. that is only true wen u consider the numerical value of the 4 digit number ... over here the numerical value is not important but the combination of different numbers is.. so 0 can be the first number ... btw my bag which had a number lock used to open with a 0000 ![Very Happy :D](./images/smilies/grin.png)
![Very Happy :D](./images/smilies/grin.png)