There is a row of street lamps on the street, a total of 40. The distance between two adjacent lamps was originally 45 meters, but now it is changed to 30 meters. How many street lamps can there be without moving.
街道上有一排路灯，共40根，每相邻两根距离原来是45米，现在要改成30米，可以有多少根路灯不需要移动．
<gadget id="calculator">2 * 3 * 3 * 5</gadget>
<output>90</output>

<gadget id="calculator">40 / 90</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">45 * (4/9)</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<result>21</result>