题目

某校在九年级学生中随机抽取了若干名学生参加“平均每天体育运动时间”的调查，根据调查结果绘制了如下不完整的频数分布表和频数分布直方图．频数分布表运动时间t/min频数频率40.170.175a0.3590.2256b合计n1请根据图表中的信息解答下列问题： （1） 频数分布表中的a=，b=，n=； （2） 请补全频数分布直方图； （3） 若该校九年级共有480名学生，试估计该校九年级学生平均每天体育运动时间不低于120 min的学生人数．Making Short Videos“A picture is worth a thousand words or so”, they say. Well, motion (运动) pictures can contain even more memories. 1.Here are some apps you can use to make your own short videos.Qupeiyin.cnReciting lines from movies is an effective and classic way to learn English. So what if you could dub(配音) recordings accompanied by movie clips(剪辑) and then share them with friends? 2.You name it. By contributing your voice, you can either mimic(模仿) the original soundtrack or create something completely new of your own.Shorts3.With the help of the Shorts app, you can make pictures in your album into a slide show. Choose from any of the off-the-shelf themes---“holiday”, “travel”, “friendship” and “party” for example—each matched with its own theme music and slide background. But if you’re not satisfied with the combinations, feel free to do a little change by adding text to the pictures or replacing the music with something in your own playlist.Viva VideoVideo making and editing once seemed awfully hard. 4.But this app will ease you into the field with straight-forward functions and clear direction to help you “create your own video story”. Apart from filter, stickers and text, the coolest part of this app is that you can write the narratives yourself and add your own voice to the video. 5.Viva Video requires a relatively powerful phone to run smoothly.A. But here is a little reminder.B. That’s why short videos are becoming popular.C. These apps have a variety of identifications (识别).D. This app has movies, cartoons, lectures, TV series.E. Newbies (网络新手) and amateurs didn’t dare to even give it a try.F. Videos and pictures aren’t only for separate purposes.G. Video making and editing is what Apple fans want to try.