The traffic lights at an intersection change from green, yellow, and red in sequence. It takes 40 seconds from green light to yellow light, 2 seconds from yellow light to red light, and 48 seconds from red light to green light. If from 9:45 to 10:15, how many times did the signal light change?
某路口的交通信号灯由绿、黄、红三色依次转换．绿灯到黄灯需40秒，黄灯到红灯要2秒，红灯到绿灯要48秒．如果从9时45分到10时15分，这个信号灯共转换了多少次？
<gadget id="calculator">40 + 2 + 48</gadget>
<output>90</output>

<gadget id="calculator">1_800 / 90</gadget>
<output>20</output>

<result>20</result>