Question

There are some red and blue balls in a bag of 21 balls and the probability of picking 2 red balls out in a row is 1/14 how many red balls are there?

Answer 1

Answer:

6 red balls

Step-by-step explanation:

The probability in the first pick

6/21

The probability in the second pick (without replacement)

5/20

the requested probability

(6/21)(5/20) = 30/420

simplification

30/420 = 3/42 = 1/14

Hope this helps

Answer 2

Answer:

6 red balls.

Step-by-step explanation:

If there are x red balls then

probability of 2 red balls

= x/21 * (x - 1)/20 = 1/14

x^2 - x / 420 = 1/14

x^2 - x = 30

x^2 - x - 30 = 0

(x - 6)(x + 5) = 0

x = 6.