# [SOLVED] Probability

• Sep 25th 2008, 09:45 PM
fabxx
[SOLVED] Probability
A list of numbers consists of p positive and n negative numbers. If a number is picked at random from this list, the probability that the number is positive is (3/5). What is the value of (n/p)?

a) 3/8
b) 5/8
c) 2/3
d) 3/2
e) 8/3

- - - -521
• Sep 25th 2008, 09:50 PM
mr fantastic
Quote:

Originally Posted by fabxx
A list of numbers consists of p positive and n negative numbers. If a number is picked at random from this list, the probability that the number is positive is (3/5). What is the value of (n/p)?

a) 3/8
b) 5/8
c) 2/3
d) 3/2
e) 8/3

- - - -521

$\frac{p}{p+n} = \frac{3}{5} \Rightarrow \frac{\frac{p}{n}}{\frac{p}{n} + 1} = \frac{3}{5} \, ....$
• Sep 25th 2008, 09:52 PM
fabxx
Quote:

Originally Posted by mr fantastic
$\frac{p}{p+n} = \frac{3}{5} \Rightarrow \frac{\frac{p}{n}}{\frac{p}{n} + 1} = \frac{3}{5} \, ....$

Why $\frac{p}{p+n} = \frac{3}{5}$? Thanks
• Sep 25th 2008, 09:53 PM
mr fantastic
Quote:

Originally Posted by fabxx
Why [tex]\frac{p}{p+n} = \frac{3}{5} ? Thanks

Number of positive numbers divided by the total number of positive and negative numbers.