A person rode a bicycle in northward direction then turned left and rode 3 km,…
2016
A person rode a bicycle in northward direction then turned left and rode 3 km, and again turned left and rode 2 km. He found himself exactly 3 km west of the starting point. How far did he ride northward initially?
- A.
2 km
- B.
3 km
- C.
5 km
- D.
1 km
Attempted by 105 students.
Show answer & explanation
Correct answer: A
Solution: Use coordinates to track the moves.
Start at (0, 0). After riding north x km the position is (0, x).
Turning left from north faces west; riding 3 km moves to (-3, x).
Turning left again faces south; riding 2 km moves to (-3, x - 2).
The final point is given as exactly 3 km west of the start, i.e. (-3, 0).
Set the y-coordinate equal: x - 2 = 0, so x = 2 km.
Answer: 2 km.