The digital sum of a number is the sum of its digits. For how many of the positive integers 24-80 inclusive is the digital sum a multiple of 7?
Choose the correct choice from the following options.
A) 7 B) 9 C) 14 D) 16 E) 20
is there other way than just listing?   25   34   43   52   59   61   68   70   77   9 ways..   9
<result>B</result>
The digital sum of a number is the sum of its digits. For how many of the positive integers 24-80 inclusive is the digital sum a multiple of 7?