Question

A bag contains only red and blue marbles. Yasmine takes one marble at random from the bag. The probability that she takes a red marble is 1 in 5. Yasmine returns the marble to the bag and adds five more red marbles to the bag. The probability that she takes one red marble at random is now 1 in 3. How many red marbles were originally in the bag?

A. 3 red
B. 5 red
C. 10 red
D. 2 red

Answer 1

Oops i forgot to put i though B was the right answer ( B. 5 red

Answer 2

thought ^^

Answer 3

r/(r+b) = 1/5
(r+5)/(r+5+b) = 1/3

r=5

you are correct