What least number should be added to 1536, so that the sum is completely divisible by 21?
Choices
A) 16
B) 17
C) 18
D) 19
E) 20

Rationale: "1536 ÷ 21 = 73 reminder - 3 3 + 18 = 21 hence 18 should be added to 1536 so that the sum will be divisible by 21 answer : c"
Answer: C