see
http://www.jiskha.com/display.cgi?id=1232417324
A bag soccer balls contains 8 balls with black design and 7 balls with red design with no other types of soccer balls. Coach graves reaches into the bag and randomly pulls out two soccer balls.
please check my answer
a) explain these events are either dependent or independent.
i think this is independent because the coach just randomly chooses the ball.
b) what is the propability both of the balls will be the ame design color?
is it 98/15.....
3 answers
The result of the second reach into the bag depends on the result of the first reach.
For example if the coach pulled a black one first, then for the second there would be 7 black and 7 red.
probability first one black = 8/15
then probability second one black = 7/14
so 8/15 * 7/14 for both black
probability first one not black = 7/15
probability second one not black = 6/14
so 7/15 * 6/14 for both white
add those two.
8/15 * 7/14 + 7/15 * 6/14
= (1/15)(56/14 + 42/14) = (1/15)(98/14)
= 98/210 = 49/105
For example if the coach pulled a black one first, then for the second there would be 7 black and 7 red.
probability first one black = 8/15
then probability second one black = 7/14
so 8/15 * 7/14 for both black
probability first one not black = 7/15
probability second one not black = 6/14
so 7/15 * 6/14 for both white
add those two.
8/15 * 7/14 + 7/15 * 6/14
= (1/15)(56/14 + 42/14) = (1/15)(98/14)
= 98/210 = 49/105
Oh, 49/105 = 7/15
4 answers