math help
posted by may ann on .
1. A bag contains red, blue, green, and yellow marbles. Seth takes a marble from the bag without looking, records the color of the marble, and then puts the marble back in the bag. He repeats the process until he has recorded the colors of 35 marbles. The chart below shows the results of his experiment.
outcome: red blue green yellow
frequency:10 5 13 7
Use the results of this experiment to find each probability. Write each answer as a fraction in lowest terms.
a. Find the experimental probability that the next marble he chooses is yellow.
b. Find the experimental probability that the next marble he chooses is either blue or red.

Experimental probability
=(observed frequency)/size of sample space
which leads to
P(red)=10/35=2/7
P(blue)=5/35=1/7
... etc
also, since these probabilities are complementary, we can conclude that P(blue or red)=P(blue)+P(red)
Try to work out the numbers and post for checking if you wish.