Math

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

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

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  2. thought ^^

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

    r=5

    you are correct

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