The digital sum of a number is the sum of its digits. For how many of the positive integers 24-130 inclusive is the digital sum a multiple of 7?
Select.
A) 7 B) 8 C) 14 D) 16 E) 20
is there other way than just listing?   25   34   43   52   59   61   68   70   77   86   95   106   115   124   14 ways..   14
<result>C</result>
The digital sum of a number is the sum of its digits. For how many of the positive integers 24-130 inclusive is the digital sum a multiple of 7?