If 3c2933k is divisible by both 5 and 11, where c and k are single-digit natural numbers, then c + k = ______.

Correct option is C

Given:
The number which is divisible by 5 and 11 = 3c2933k
Concept Used:
Divisibility rule of 5 - Last digit either 0 or 5.
Divisibility rule of 11 - (the sum of odd digits - sum of even digits) = 0 or multiple of 11.
Solution:
In 3c2933k to be divisible by 5 , k should either be 0 or 5 but k cannot be 0 as given that c and k are natural numbers, then
If k =5 then
(3+2+3+5)- (c+9+3)= 0 or 11
13 - 12 -c = 0 or 11
1- c =0 or 11 hence c= 1
If k=5,c=1 , sum =6