+738 One day, River writes down the numbers 1,2,...,999
River chooses one of the digits written down at random. What is the probability that River chooses a 7?
Thank you and please provide an explanation!
:)
+639 OK Here is my best shot :D
There are 280 numbers contain the digit 7 between 0 and 999.
So 280/999
Here to help
:D
If repeated digits are counted, such as 77, 777.....etc, then there are 300 sevens between 1 and 999.
If repeated digits are NOT counted, then there are 271 sevens between 1 and 999.
Then, the probability is either 300 / 999 or 271 / 999.
+129852 I get a slightly different result
The number of digits written down =
9 + 2(99 - 10 + 1) + 3(999 - 100 + 1) =
9 + 2 ( 90) + 3(900) =
2889
The number of 7's that are written down =
10*10 + 10(10) + 100 = 300
So.....the probability of selecting a "7" = 300 / 2889 = 100/963
+639 Ahhhh wait CHphill I'm doing an AOPs online course and I remember getting this question right in fact you are right the answer is indeed 100/963
Great work as usalll!
Here to help
:D
