1994 AHSME Problems/Problem 15
Problem
For how many in is the tens digit of odd?
Solution
Let . So . The first digit of it the hundreds place digit which means that is the tens and ones digit together. We note that will always be even. So in order for to have an odds tens digit, then must carry and have an odd tens digit. We note that can only equal either or for this to happen. The total number of positive integers less than or equal to that have or as the units digit is
--Solution by TheMaskedMagician
See Also
1994 AHSME (Problems • Answer Key • Resources) | ||
Preceded by Problem 14 |
Followed by Problem 16 | |
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 • 26 • 27 • 28 • 29 • 30 | ||
All AHSME Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.