There are eight threes in the first fifty digits of pi, not including the first three before the decimal point.
Here is an example below with the threes in bold.
3.14159265358979323846264338327950288419716939937510
51. 51. 51. 51.
Seventeen, with a remainder.
Currently (Sept 2014), the number of digits is 10 trillion (and fifty).
To determine how many places are in fifty million, you can look at the number of digits in the number. Fifty million is written as 50,000,000, which has eight digits. Therefore, there are eight places in fifty million, corresponding to the units, tens, hundreds, thousands, ten-thousands, hundred-thousands, millions, and ten-millions.
27 threes are in 81
51. 51. 51. 51.
Not counting the three in the ones place, there are 100229.
100230, which includes the first one to the left of the decimal point.
Fifty threes are in 150.
We only use 10 digits (0 through 9), so I would say, there is one of them.
There are 100229 threes and 100106 nines. A table of all the digit frequencies can be found at http://www.super-computing.org/pi-decimal_current.html
Not counting the 3 in the ones place, there are 100229 threes and 100106 nines.
About 100,000 of each.
Seventeen, with a remainder.
Fifteen. 3, 13, 23, 30, 31, 32, 33*, 34, 35, 36, 37, 38, 39, 43. Note 33 has two threes.
Currently (Sept 2014), the number of digits is 10 trillion (and fifty).
27 threes are in 81