Two Classic Test Problems

These two problems almost always show up on standardized math test in 9th grade and up.  Can you work them?  Back with answers  tomorrow.

1.  A bag contains 3 green marbles, 5 blue marbles, and 2 yellow marbles. One marble is drawn from the bag.  Find the  probability that the marble is blue.

ANSWERS!!!!!!!!!!!!!!!!   Thanks for the emails.  Most of you were right on!  If you didn’t write in, check your answers now.

1.  10 Total Marbles.  Probability of selecting a green marble is 2 out of 10, or 2/10, or 1/5.  Pr(Blue) is 5/10 or 1/2.  Pr(Yellow) =2/10=1/5.  

2.  Mr. A’s 1st Period class has 5 girls and 7 boys.  Ms. Z’s 1st Period   class has 8 girls and 7 boys.  One student is to be selected at    random from each class to go to the guidance office to pick up copies of next semester’s course offerings.  Find the probability that Mr. A and Ms. Z each pick a boy.

ANSWER:

Probability of Mr. A choosing a boy is 7 out of 12 or 7/12.  Pr (Mrs.Z selecting a boy)=7/15.  Pr (Both selecting boys)= 7/12 times 7/15 or 49/180.    Or 1/3.67. Or 0.27222.  Or a little less than 1/3.

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