Saturday

November 22, 2014

November 22, 2014

Posted by **Anonymous** on Monday, February 18, 2013 at 8:22am.

Two balls are drawn. If probability of both being green is 1/7 find m.

- maths-urgently needed(probability) -
**Reiny**, Monday, February 18, 2013 at 8:44amI will assume the first ball drawn is NOT returned.

prob(2green) = (n/(9+n) * ((n-1)/(8+n)) = 1/7

7n^2 - 7n = n^2 + 17n + 72

6n^2 - 24n - 72 = 0

n^2 - 4n - 12 = 0

(n-6)(n+2) = 0

n = 6 or n = a negative, which is no good

there were 6 green balls

check:

prob(2greens) = (6/15)(5/14) = 1/7

**Answer this Question**

**Related Questions**

Basic Mathematics - A bag contains 2 red balls, 3 blue balls and 5 green balls. ...

8th Grade Probability - A box contains 6 red balls, 4 white balls, and 5 green ...

Math - A bag contains 5 balls,8 white balls, 9 green balls,7 blue balls& 6 ...

math - A box contains 6 red balls, 4 white balls, and 5 green balls. If three ...

probability - a bag contains 7 red balls, 4 green balls and 5 yellow balls. what...

8th grade math - A box contains 6 red balls, 4 white balls, and 5 green balls. ...

Probability again - A box contains 6 red balls, 4 blue balls, and 2 green balls...

probability - A jar contains 3 red balls and 2 green balls. You draw one ball at...

Math - A bag contains 5 red balls and 4 white balls. Two balls are drawn at ...

Math - A bag contains 5red balls and 4 white balls. Two balls are drawn at ...