问题
单项选择题
A certain clock marks every hour by striking a number of times equal to the hour and the time required for a stroke is exactly equal to the time interval between strokes. At 6:00 the time lapse between the beginning of the first stroke and the end of the last stroke is 22 seconds. At 12:00, how many seconds elapse between the beginning of the first stroke and the end of the last stroke ？（）
A．72
B．50
C．48
D．46
E．44
答案
参考答案：D
解析：
由题意可知敲击持续的时间与两次敲击之间的间隔时间相同，设该时间为32秒，注意到间隔的次数比敲击的次数少1次，则6:00该钟表共敲击6次，间隔为5次，由题意可得到F面的方程：(6+5)x=22→x=2因此12:00时的敲击与间隔时间共为(12+11)×2=46秒