2005 Alabama ARML TST Problems/Problem 4
Problem
For how many ordered pairs of digits is a multiple of ?
Solution
A number is divisible by if it is divisible by and . A number is divisible by if its last two digits are divisible by , so . A number is divisible by if the sum of its digits is , so
- - 3 solutions
- - 4 solutions
- - 3 solutions
- - 3 solutions
- - 4 solutions
These sum to .
See also
2005 Alabama ARML TST (Problems) | ||
Preceded by: Problem 3 |
Followed by: Problem 5 | |
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