题干

某学习小组的同学做摸球实验时,在一个暗箱里放了多个只有颜色不同的小球,将小球搅匀后任意摸出一个,记下颜色并放回暗箱,再次将球搅匀后任意摸出一个,不断重复.下表是实验过程中记录的数据:

摸球的次数m

300

400

500

800

1000

摸到白球的次数n

186

242

296

483

599

摸到白球的频率

n
m

0.620

0.605

0.592

0.604

0.599

请估计从暗箱中任意摸出一个球是白球的概率是____

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    Research suggests that at least 64% of people now spend up to four hours daily of spare time in front of a screen. Just as TV watching has been linked to higher chances of being fat and getting diseases, this extra sedentary time is bad news for our health.

    ⒈Choose outdoor activities over technology

    When you're at home, make it a rule that you can't be online if the sun is shining. Instead, you have to go for a walk, ride a bike, swim or get some other kind of healthy, physical activity for at least an hour before you can pull out your phone or tablet, or take a seat at the computer. This rule should be fit for everyone in your family.

    ⒉Limit social media use

    Social networks have changed computer and mobile use for people of all ages. Whether it's Facebook, Twitter, Instagram or Snapchat. Limit the amount of time you spend on social media. Avoid aimless browsing(浏览) and give your time online a purpose research holidays or catch up on the news of the day. Then log off.

    ⒊Save time for reading

    Challenge yourself to read at least 30 pages of a great book before you check your computer or mobile phone. Pick the right reading material and you'll soon find you've discovered an enjoyable pastime.

    ⒋Create projects for yourself

    It's amazing how much you can achieve when you're not glued to (长时间盯着) a screen. Do a list of one-hour evening projects. Some suggestions are organizing kitchen cupboards, cleaning your bedroom. Then try to do one each evening.