In a bag of 20 marbles, 4 are blue. what is the probability that one taken at random will not be blue?

Your answer is 4/5, which is 80% or 0.8

If there are 20 marbles in total in the bag, and 4 blue ones, that means that the probability of taking a blue one is 4/20.

This means that the probability of not taking a blue one is 1 - 4/20, or 20/20 - 4/20, which equals 16/20 = 4/5

I hope this helps! Let me know if you have any questions :)

403 pages left, then she had read (481 - 403) = 78 pages in that 1.5 hours.
(78 pages / 1.5 hours) = (78 / 1.5) (pages/hours) = 52 pages per hour.
The whole book is 481 pages.
To read the whole book at the same rate will take (481 pages) / (52 page/hour) = (481 / 52) (hour) = 9.25 hours. 
9 hours 15 minutes