Difference between revisions of "2013 AMC 10A Problems/Problem 7"
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Here, we simply count how many ways we can do one, multiply by <math>2</math>, and then add to the previous. | Here, we simply count how many ways we can do one, multiply by <math>2</math>, and then add to the previous. | ||
− | + | Assume the mathematics course is algebra. This means that we can choose <math>2</math> of History, Art, and Latin, which is simply <math>\dbinom{3}{2} = 3</math>. If it is geometry, we have another <math>3</math> options, so we have a total of <math>6</math> options if only one mathematics course is chosen. | |
Thus, overall, we can choose a program in <math>6 + 3 = \boxed{\textbf{(C) }9}</math> ways | Thus, overall, we can choose a program in <math>6 + 3 = \boxed{\textbf{(C) }9}</math> ways |
Revision as of 15:47, 28 January 2017
Contents
Problem
A student must choose a program of four courses from a menu of courses consisting of English, Algebra, Geometry, History, Art, and Latin. This program must contain English and at least one mathematics course. In how many ways can this program be chosen?
Solution 1
Let us split this up into two cases.
Case : The student chooses both algebra and geometry.
This means that courses have already been chosen. We have more options for the last course, so there are possibilities here.
Case : The student chooses one or the other.
Here, we simply count how many ways we can do one, multiply by , and then add to the previous.
Assume the mathematics course is algebra. This means that we can choose of History, Art, and Latin, which is simply . If it is geometry, we have another options, so we have a total of options if only one mathematics course is chosen.
Thus, overall, we can choose a program in ways
Solution 2
We can use complementary counting. Since there must be an English class, we will add that to our list of classes for remaining spots for the classes. We are also told that there needs to be at least one math class. This calls for complementary counting. The total number of ways of choosing classes out of the is . The total number of ways of choosing only non-mathematical classes is . Therefore the amount of ways you can pick classes with at least one math class is ways.
See Also
2013 AMC 10A (Problems • Answer Key • Resources) | ||
Preceded by Problem 6 |
Followed by Problem 8 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AMC 10 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.