在长 1.5 km 的公路一边，等距离种树（两端都种），原计划每 10 m 种一棵并已放好种树的标记物，后来改成每 12 m 种一棵，如果在种树地点安放标记物，那么不用移动的标记物有几个？
Along one side of a 1.5 km long road, trees are to be planted at regular intervals (at both ends). The original plan was to plant one tree every 10 metres, and markers had already been placed accordingly; however, this was later changed to one tree every 12 metres. If markers are placed at the planting locations, how many markers will remain in place without needing to be moved?

如图，街道ABC在点B处拐弯，在街道的一侧要等距离安装路灯，要求在点A、B、C处各安装一盏路灯，问：最少要安装多少盏路灯？

As shown in the diagram, street ABC bends at point B. Street lamps are to be installed at equal intervals along one side of the street. One street lamp is to be installed at each of points A, B and C. How many street lamps must be installed at the very least?