Let the boy starts from point A and travels 4 km towards south to reach B and then takes a left turn and travels another 3 km east wards to finally reach point C. Thus, (AC)2=(AB)2+(BC)2 ⇒ (AC)2=(4)2+(3)2 ⇒ (AC)2=16+9=25 ⇒ AC=√25=5 km ∴ He is 5 km in the south-east direction from his original position.