juliewang
幼苗
共回答了19个问题采纳率:100% 举报
1.四点多少分时,时针和分针成一条直线?
(5*4)/(1-5/60)
=20/(1-1/12)
=20/(11/12)
=20*(12/11)
=240/11
=21又(9/11)分
(5*4+30)/(1-5/60)
=50/(1-1/12)
=50/(11/12)
=50*(12/11)
=600/11
=54又(6/11)分
四点21又(9/11)分和四点54又(6/11)分时,时针和分针成一条直线.
2.一个人外出办事,此时为三点多,时针和分针的夹角为55°,回来时看钟表,此时还不到四点钟,但,分针和时针的夹角依旧为55°,求用了多少时间?
外出时:
(15-55°*(60/360°))/(1-5/60)
=(15-55/6)/(1-1/12)
=(15-55/6)/(11/12)
=(15-55/6)*(12/11)
=(180-110)/11
=70/11
=6又(4/11)分
回来时:
(15+55°*(60/360°))/(1-5/60)
=(15+55/6)/(1-1/12)
=(15+55/6)/(11/12)
=(15+55/6)*(12/11)
=(180+110)/11
=290/11
=26又(4/11)分
用了多少时间:26又(4/11)分-6又(4/11)分=20分钟
3.五点五十分,时针和分针的夹角为多少度?
(50-5*5-50*(5/60))*(360°/60)
=(25-50*(1/12))*6°
=150°-25°
=125°
1年前
7