Question

A bag contains 4 blue marbles, 5 green marbles and 3 yellow marbles. How many blue marbles should you add to the bag so that the probability of drawing a marble is 0.80

Answer 1

ADD 28 blue marbles. Added for total of 32/40= 0.80

Explanation:

4/12 or 1/3 (33%) for original amount

X/X+8=.8

X=.8 x (X+8)

X=

Sorry I do not remember how to complete this equation so did it by substituting numbers until solution was .80

Need a total of 32/32+8 (40) =0.8 or 80% chance

So need to add

28 blue marbles.