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?

Question

Mathematics

Jakobe Church

8 April, 02:53

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?

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Luis Bradley · Answer 1

R / (r + g) = 1/5 = = = 5r = r + g = = = 4r = g

(r + 5) / (r + 5 + g) = 1/3 - - - 3r + 15 = r + 5 + g

2r = g - 10 ... 4r = 2g - 20

g = 2g - 20

g = 20 ... 4r = g ... r = 5

20 green and 5 red