🎥 Video solution / Text Solution of this question is given below:
1st round (forward starting from 1):
1, 4, 7, 10, …, 49 → all multiples of form 1 + 3k
Unanswered after first round:
2, 3, 5, 6, 8, 9, …, 50
2nd round (reverse starting from 50):
50, 47, 44, 41, …, 2 → all backwards with difference −3
Unanswered after second round:
3, 6, 9, 12, …, 48
3rd round (forward starting from 3):
3, 6, 9, …, 48 → finishing at 48
So the last answered question = 48.