Note on this question: there is a mismatch between the English and Hindi versions of this question as officially set by UGC. The English text given here describes only THREE legs of the walk (South 30 m, left turn + 40 m, left turn + 30 m, ending at point B). However, the Hindi version of the same question includes a FOURTH leg that is missing from the English text: after reaching point B, the man turns left again and walks 60 metres further. Because the two language versions describe different journeys, UGC officially dropped this question. For learning purposes, here is how the given answer is derived using the complete, 4-leg version of the journey (matching the Hindi text):
Step 1: The man starts at point A facing South and walks 30 m South.
Step 2: He turns left. If you are facing South, a left turn makes you face East. He walks 40 m East.
Step 3: He turns left again. Facing East, a left turn makes you face North. He walks 30 m North. This is point B.
Step 4: (this leg is present only in the Hindi version) He turns left again. Facing North, a left turn makes you face West. He walks 60 m West.
Step 5: Now calculate the net displacement.
Net North-South displacement = 30 m South − 30 m North = 0 (the southward and northward walks cancel out).
Net East-West displacement = 40 m East − 60 m West = 20 m West (since 60 m West is more than 40 m East, the net direction is West).
So the man ends up exactly 20 metres to the West of point A, which matches the given answer 20 meters West. (Note: if only the 3-leg English version is used, the final position would be 40 m East of A, which does not match any option — this confirms the English text is incomplete and the question was correctly dropped by UGC.)