Saved Bookmarks
| 1. |
What is the probability that the sum of any two different single digit natural numbers is a prime number? |
|
Answer» We know single digit natural number are from `1` to `9`. Now, the maximum sum that we can get is `9+8=17` as we have to use different numbers. Now, possible two digits having a sum equal to prime number are, `(1+2),(1+4),(2+3),(1+6),(2+5),(3+4),(2+9),(3+8),(4+7),(5+6),` `(4+9),(5+8),(6+7),(8+9)`. So, there are `14` possible values. Now, number of ways selecting these `2` digits from `9` digits is `C(9,2)`. `:.` the required probability ` = 14/(C(9,2)) = 14/36 = 7/18` |
|