Browse · MATH
Printjmc
prealgebra intermediate
Problem
If is split after the third digit into a three-digit integer and a one-digit integer, then the two integers, and , have a common factor greater than one. The years and each have this same property, too. What is the first odd-numbered year after that has this property?
Solution
We note that has the property: since the sum of the digits of 201, , is divisible by , is itself divisible by . We must now check whether any odd-numbered years before have the property. is not divisible by the prime , so does not have this property. Likewise, the sum of the digits of is , which is not divisible by , so and are relatively prime. Clearly does not have the desired property since every natural number is relatively prime to . Thus, the first odd-numbered year after that has the desired property is .
Final answer
2013