How well do you know prime numbers?
Let the number of 3 digit prime numbers be .
Let the number of 3 digit prime numbers having only 2 distinct digits be .
What is the value of ?
Notes
- 123 has 3 distinct digits but 222 has only one.
The answer is 97.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
A little Python script:
gives us 9 7 .
Note: this prime function only works well for n>2. Luckily, we are only dealing with n>100 in this problem.