Correct Answer - Option 3 : 27th
In a class of 45 students, a boy is ranked 20th.
When two boys joined, then number of students becomes 47.
And the rank of the boy dropped by one.
So, the boys new rank is 21st.
The boys new rank from the end = (47 - 21 + 1)
= 48 - 21
Hence, ‘27th’ is the correct answer.