Question

A bag contains only blue and red marbles.Asman takes 1 marbles at random out of a bag. Probability that she takes a red marble out of the bag is One in five Asman returns the marble to the bag and adds 5 more red marbles to the bag. Probability that she takes one red marble out of the bag is now one in three how many red marbles were originally in the bag

Answer 1

At first situation, ratio = x/y = 1/5
5x = y  -------Equation (i)
Now, after adding 5 more red, it is = x + 5 / y+5 = 1/3
y+5 = 3(x + 5)
y + 5 = 3x + 15
y - 3x = 15 - 5

Substitute the value of y from equation (1), 
5x - 3x = 15 - 5
2x = 10
x = 10/2
x = 5

Originally, There were 5 red marbles in the bag

Hope this helps!