Here's the question -
A bag contains (n=7) balls. n are yellow, 7 are white. John will take a ball from the bag. He will look at its colour and then put it back.
1) write an expression, in temrs of n, for the probability that john will take a white ball.
2) bill states that the probability that john will take a white ball is 2/5. Prove this is not correct.
Please help! Thanks.
A bag contains (n=7) balls. n are yellow, 7 are white. John will take a ball from the bag. He will look at its colour and then put it back.
1) write an expression, in temrs of n, for the probability that john will take a white ball.
2) bill states that the probability that john will take a white ball is 2/5. Prove this is not correct.
Please help! Thanks.
-
1.
7/(n+7)
2
7/(n+7)=2/5
cross multiplying
35=2n+14
2n=21
n=21/2, but n cannot be a fraction, so he's wrong
7/(n+7)
2
7/(n+7)=2/5
cross multiplying
35=2n+14
2n=21
n=21/2, but n cannot be a fraction, so he's wrong
-
1. probability of taking a white ball = number of white ball / total balls
= 7 / (n+7)
2. if 7 / (n+7) = 2/5
35 = 2(n + 7)
n =35/2 - 7 which is a fraction...
so 2/5 is not correct.
= 7 / (n+7)
2. if 7 / (n+7) = 2/5
35 = 2(n + 7)
n =35/2 - 7 which is a fraction...
so 2/5 is not correct.