The units digit of a three-digit number is prime. The hundreds digit is twice the tens digit. How many of these three digit numbers are prime?

Answer 1

first condition:
XX2 XX3 XX5 XX7

Second condition: hundreds is twice tens

842 632 422 212
843 ....
...
847................217

There will be 16 of those

I will leave it up to you to decide how many of those are prime numbers.
(remember, just because a number ends in an odd number, does not mean it is prime.
e.g. 633 is not prime, but 843 is prime )

Here is a list of primes:

https://primes.utm.edu/lists/small/1000.txt