Difference between revisions of "2012 AMC 10B Problems/Problem 10"
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== Problem 10 == | == Problem 10 == | ||
− | How many ordered pairs of positive integers (M,N) satisfy the equation <math>\frac {M}{6}</math> = <math>\frac{6}{N}</math> | + | How many ordered pairs of positive integers <math>(M,N)</math> satisfy the equation <math>\frac {M}{6}</math> = <math>\frac{6}{N}</math>? |
− | <math> \textbf{(A)}\ 6\qquad\textbf{(B)}\ 7\qquad\textbf{(C)}\ 8\qquad\textbf{(D)}\ 9\qquad\textbf{(E)}\10 </math> | + | <math> \textbf{(A)}\ 6\qquad\textbf{(B)}\ 7\qquad\textbf{(C)}\ 8\qquad\textbf{(D)}\ 9\qquad\textbf{(E)}\ 10 </math> |
[[2012 AMC 10B Problems/Problem 10|Solution]] | [[2012 AMC 10B Problems/Problem 10|Solution]] | ||
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== Solution == | == Solution == | ||
Line 18: | Line 16: | ||
Now you find all the factors of 36: | Now you find all the factors of 36: | ||
− | 1 | + | <math>1\times36=36</math> |
− | 2 | + | <math>2\times18=36</math> |
− | 3 | + | <math>3\times12=36</math> |
− | 4 | + | <math>4\times9=36</math> |
− | 6 | + | <math>6\times6=36</math>. |
Now you can reverse the order of the factors for all of the ones listed above, because they are ordered pairs except for 6*6 since it is the same back if you reverse the order. | Now you can reverse the order of the factors for all of the ones listed above, because they are ordered pairs except for 6*6 since it is the same back if you reverse the order. | ||
− | <math>4 | + | <math>4\cdot 2+1=9</math> |
+ | |||
+ | <math>\boxed{\textbf{(D)}\ 9}</math> | ||
− | + | ==See Also== | |
− | + | {{AMC10 box|year=2012|ab=B|num-b=9|num-a=11}} | |
+ | {{MAA Notice}} |
Revision as of 15:19, 28 August 2020
Problem 10
How many ordered pairs of positive integers satisfy the equation = ?
Solution
=
is a ratio; therefore, you can cross-multiply.
Now you find all the factors of 36:
.
Now you can reverse the order of the factors for all of the ones listed above, because they are ordered pairs except for 6*6 since it is the same back if you reverse the order.
See Also
2012 AMC 10B (Problems • Answer Key • Resources) | ||
Preceded by Problem 9 |
Followed by Problem 11 | |
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 |
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