Don L. answered • 04/21/16
Tutor
5
(18)
Fifteen years teaching and tutoring basic math skills and algebra
Hi Lydia, the probability of picking three green marbles and then one blue marble without replacement is given by:
5/12 * 4/11 * 3/10 * 7/9, which equals about .035 or 3.5 percent.
Looking at the answers provided:
a) 5C3 * 7C1 / 12C4
5C3 = 10, 7C1 = 7, and 12C4 = 495
10 * 7 / 495 = about .1414
b) 5P3 * 7P1 / 12P4
5P3 = 60, 7P1 = 7, 12P4 = 11880
60 * 7 / 11880 = about .035 or 3.5 percent
c) 5C2 * 7P2 / 12
5C2 = 10, 7P2 = 42
10 * 42 / 12 = 35
d) 5C3 * 7P1 / 12
5C3 = 10, 7P1 = 7
10 * 7 / 12 = 5.83
The answer is b.
Questions?
Don L.
tutor
Hi Lydia, you are starting with 12 marbles total, 5 of which are green. Therefore, there are 5 ways to pick a green marble from the 12 marbles in the jar.
That leaves 11 marbles, 4 of which are green. There are 4 ways to pick a green marble from the 11 marbles in the jar.
That leaves 10 marbles, 3 of which are green. There are 3 ways to pick a green marble from the 10 marbles in the jar.
That leaves 9 marbles, 7 of which are blue. There are 7 ways to pick a blue marble from the 9 marbles in the jar.
Questions?
Report
04/21/16
Lindsay D.
ooh okay that makes sense i was not going about this the right way.
Report
04/21/16
Lindsay D.
04/21/16