Q.Rahul starts walking facing East. He walks 5 km, then turns right and walks 3 km, then turns right again and walks 5 km. How far is he now from his starting point, and in which direction?

Track the net East-West and North-South displacement leg by leg, remembering that a right turn is a 90-degree clockwise turn.

Starting facing East:

• Leg 1: walks 5 km East.
• Turns right (a right turn from East, turning clockwise, points him South).
• Leg 2: walks 3 km South.
• Turns right again (a right turn from South, turning clockwise, points him West).
• Leg 3: walks 5 km West.

Now add up the net displacement in each pair of opposite directions. East-West: he walked 5 km East (Leg 1) and 5 km West (Leg 3) — these exactly cancel, leaving a net East-West displacement of 0. North-South: he walked 3 km South (Leg 2), the only leg in that direction, so the net North-South displacement is 3 km South. …

Forgetting that 'turning right' means a DIFFERENT compass direction depending on which way one is currently facing (a right turn from East gives South, but a right turn from North would give East) is the most common error — always work out the new fa …