Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and the Yahoo Answers website is now in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
Math Question on Expected Value?
Ten cards are numbered 1 through 10. Two of these cards are chosen randomly(without replacement) and the numbers are then added. Find the expected value of this sum.
1 Answer
- 8 years agoFavorite Answer
There are 90 combinations: (1,2), (1,3), ..., (1,10), (2,1), (2,3), ..., (2,10), ..., (9,10). The expected value is:
[ (1+2)+(1+3)+...(1+10) + (2+1)+(2+3)+...+(2+10) + ... + (9+10)] / 90
= [ 3+4+...+11 + 3+5+...+12 + ...] / 90
= [ 63 + 71 + 79 + ... + 135 ] / 90
= 990 / 90
= 11