Correct Answer - Option 4 : 55
Ajay ranked sixteenth from the top and twenty-ninth from the bottom among those who passed an examination.
Total number of boys who passed the examination = 16 + 29 - 1
= 45 - 1
= 44
Six boys did not participate in the competition and five failed in it.
Therefore, total number of boys in the class = 44 + 6 + 5
= 55
Hence, '55' is the correct answer.