X is 7th from the top while Y is 16th from the bottom in the class ranking. If they interchange their positions, then X becomes 21st from the top. What will be the position of Y from the bottom?
Answer & explanation
Correct answer: option 4
X is 7th from the top and Y is 16th from the bottom.
It means there are 6 students above X and 15 students below Y.
Now, after interchanging their positions,
X becomes 21st from the top means there are 20 students above X.
But it is clear that there are 6 students above Y, so,
Students in between X and Y = 20 - 6 - 1 (Y) = 14 - 1 = 13.
Position of Y from bottom = 15 + 1 (X) + 13 + 1 (Y) = 30th.