One day Prakash left home and walked 10 km towards south, turned right and…
2015
One day Prakash left home and walked 10 km towards south, turned right and walked 5 km, turned right and walked 10 km and turned left and walked 10 km. How many km will he have to walk to reach his home straight?
- A.
30
- B.
10
- C.
20
- D.
15
Attempted by 47 students.
Show answer & explanation
Correct answer: D
Key idea: find the straight-line displacement (not the total path length) from the starting point to the final point by tracking each move.
Place the home (starting point) at coordinates (0, 0).
Walk 10 km south → new position is (0, −10).
Turn right (west) and walk 5 km → new position is (−5, −10).
Turn right (north) and walk 10 km → new position is (−5, 0).
Turn left (west) and walk 10 km → final position is (−15, 0).
Compute the straight-line distance from (0,0) to (−15,0):
Distance = √[(−15−0)² + (0−0)²] = √(225) = 15 km.
Answer: 15 km