why don't you put some effort into it for once and try and figure it out on your own.
a four digit numbers, in range of 000-9999, is formed. Find the probability of the numbers begins and end with zero.
the ans is 19/100. how to do this?
find the probablity of the numbers contains ecxactly two non-zero digits. the ans is 243/5000 . how to do this?
If you set the first and last digits to 0, how many digits are left free to set?Spoiler:
How many different ways can each digit be set?Spoiler:
So how many ways can 2 digits be set?Spoiler:
How many possible 4 digit numbers are there total?Spoiler:
So what is the probability of a 4 digit number with the first and last digits equal to 0?Spoiler:
Another way of looking at it
How many ways can you set 2 digits with 10 numbers.Spoiler:
You are selecting a single pattern of 2 digits for the 1st and 4th slots. This is 1 out of the number above.
So the probability isSpoiler: