Probability (1 Viewer)

[cos16mh]

If the numerals 2,3,4,5,6 are randomly arranged to make a 5 digit number, what is the probability the number is:

a) an odd number less than 30000

b) an even number greater than 40000

 

[dan964]

I won't do the computation but:
(A) Pick the first digit to be 2, and then pick the last digit to be either 3 or 5, out of the remaining 4 digits.

(B) Pick the first digit to be either 4 or 5 or 6. And then from the remaining collection:

If 4 is the first digit, then you can pick 2 or 6 for the last digit out of the remaining 4
If 5 is the first digit, then you can pick 2 or 4 or 6 for the last digit.
If 6 is the first digit, then you can pick 2 or 4 for the last digit.

Expected Answers:
(A)
0.2*0.5 = 0.1

(B)
0.2*0.5+0.2*0.75+0.2*0.5
= 0.35

(show why.)