A ladder leans against a vertical wall. The top of the ladder is 9 m above the floor. When the foot of the ladder is moved 3 m farther from the wall, the top of the ladder comes down to the foot of the wall. What is the length of the ladder?

16 m
15 m
20 m
30 m

సమాధానం చూపించు & వివరణ

సమాధానం: (B) 15 m

వివరణ

Let the ladder's length be L and its foot be d m from the wall, so L² = 9² + d². After moving 3 m further the ladder lies flat along the floor, reaching the foot of the wall, so L = d + 3. Then (d + 3)² = 81 + d², i.e. 6d + 9 = 81, so d = 12 and L = 15 m.