Difference between revisions of "2004 AMC 12B Problems/Problem 4"
(New page: == Problem == An integer <math>x</math>, with <math>10\leq x\leq 99</math>, is to be chosen. If all choices are equally likely, what is the probability that at least one digit of <math>x<...) |
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Revision as of 10:07, 6 January 2009
Problem
An integer , with , is to be chosen. If all choices are equally likely, what is the probability that at least one digit of is a 7?
Solution
The digit 7 can be either the tens digit ( - 10 possibilities), or the ones digit ( - 9 possibilities), but we counted the number 77 twice. This means that out of the 90 two-digit numbers, have at least one digit equal to 7. Therefore the probability is .
See Also
2004 AMC 12B (Problems • Answer Key • Resources) | |
Preceded by Problem 3 |
Followed by Problem 5 |
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 |