Question

which no. should replace the question mark:6,21,66,201,606,?

5432
6543
1821

Answer 1

if we multiply 3 in 6 and then add 3 the answer will be 21
then again we multiply 3 in 21 and then add 3 the answer will be 66 
therefore on multiplying 3 in 606 and then adding 3 to it we get 1821 
therefore the ans is 1821

Answer 2

if we add 1 in 6 and then multiply it by 3 it will result into 21.
similarly if we add 1 in 21 and then multiply it by 3 it will result into 66.
similarly if we add 1 in 607 and multiply it by 3 it will result into 1821.
hence the correct option is 1821.