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?

Answer 1

Answer: 5 Red Marbles

The bag started with 5 Red Marbles and 20 Blue Marbles

When you add the 5 additional red marbles it becomes 10 red marbles out of 30 total marbles or 1 in 3.