2007 AMC 12A Problems/Problem 7: Difference between revisions
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* <math>a=c-2f</math> | * <math>a=c-2f</math> | ||
* <math>b | * <math>b=c-f</math> | ||
* <math>c | * <math>c=c</math> | ||
* <math>d | * <math>d=c+f</math> | ||
* <math>e=c+2f</math> | * <math>e=c+2f</math> | ||
<math>a+b+c+d+e=5c=30</math>, so <math>c=6</math>. But we can't find any more variables, because we don't know what <math>f</math> is. So the answer is <math>\textrm{ | <math>a+b+c+d+e=5c=30</math>, so <math>c=6</math>. But we can't find any more variables, because we don't know what <math>f</math> is. So the answer is <math>\textrm{C}</math>. | ||
==See also== | ==See also== | ||
{{AMC12 box|year=2007|num-b=6|num-a=8|ab=A}} | {{AMC12 box|year=2007|num-b=6|num-a=8|ab=A}} | ||
Revision as of 11:05, 22 November 2007
Problem
Let 
, and 
be five consecutive terms in an arithmetic sequence, and suppose that 
. Which of 
or can be found?
Solution
Let 
be the common difference between the terms.
, so 
. But we can't find any more variables, because we don't know what is. So the answer is 
.
See also
| 2007 AMC 12A (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 12 Problems and Solutions | |
