Discussion
If x and y are prime numbers, then which one of the following cannot equal x − y?
| (A) | 1 |
| (B) | ... |
| (C) | ... |
| (D) | ... |
| (E) | ... |
| (F) | ... |
The solution is
Posted: 09/25/2012 20:48
Help me with this ques......
Posted: 10/23/2012 15:10
Franko, have you tapped on "Show Correct Answer" after hitting Confirm? Please try that next time, then if you are still stuck, post on the discussion forum. Here the choices range from 1 to 20, so we want to list prime numbers up to 40 something (20 + 20) to substitute into x and y: 2 3 5 7 11 13 17 19 23 29 31 37 41 43
Now, try plugging in to eliminate the incorrect choices.
2 -1 =1. So (A) is out
5 - 3 = 2, so (B) is out
We can also try adding the difference to one of the prime numbers, and see if the result is also a prime number:
23 + 20 = 43, so (E) is out
14 +17 = 31, so (D) is also out.
We are left with (C) 13.
Now, try plugging in to eliminate the incorrect choices.
2 -1 =1. So (A) is out
5 - 3 = 2, so (B) is out
We can also try adding the difference to one of the prime numbers, and see if the result is also a prime number:
23 + 20 = 43, so (E) is out
14 +17 = 31, so (D) is also out.
We are left with (C) 13.
Posted: 08/19/2013 20:25
What is the definition of a prime number? Definitions would help a lot.
Posted: 08/20/2013 13:50
A prime number can only be divided by itself and 1.
Posted: 08/09/2014 10:09
Thanks