Difference between revisions of "2004 AMC 10B Problems/Problem 2"
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==Problem== | ==Problem== | ||
| − | How many two-digit positive integers have at least one 7 as a digit? | + | How many two-digit positive integers have at least one <math>7</math> as a digit? |
<math> \mathrm{(A) \ } 10 \qquad \mathrm{(B) \ } 18\qquad \mathrm{(C) \ } 19 \qquad \mathrm{(D) \ } 20\qquad \mathrm{(E) \ } 30 </math> | <math> \mathrm{(A) \ } 10 \qquad \mathrm{(B) \ } 18\qquad \mathrm{(C) \ } 19 \qquad \mathrm{(D) \ } 20\qquad \mathrm{(E) \ } 30 </math> | ||
Revision as of 20:00, 22 July 2014
Problem
How many two-digit positive integers have at least one 
as a digit?
Solution
Ten numbers (
) have as the tens digit. Nine numbers (
) have it as the ones digit. Number 
is in both sets.
Thus the result is 
.
See also
| 2004 AMC 10B (Problems • Answer Key • Resources) | ||
| Preceded by Problem 1 |
Followed by Problem 3 | |
| 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. 
