A

    I love to go biking! Two years ago I bought an exercise bike(健身脚踏车)．But soon I got bored with being at home, so I bought a used bike and started going for short rides．Now I plan day trips in my neighborhood．When you drive a car, you miss many things．It's surprising how much more you can see when you're biking．

    —Maggie

    My favorite thing to do on the weekend is to go to the beach．The beach is beautiful all through the year．I usually drive there．If the weather is cold；I wear some warm clothes and go for long walks on the beach．When the weather is hot，I enjoy swimming or lust lying in the sun.

一Barbara

    On the weekend I like to read books．If the weather is nice．I'll take a good book to the park and stay there reading for hours．I think there's nothing as enjoyable as reading a good book．

    一Bill

    Weekends are for going hiking(徒步旅行)with my parents．We live near some beautiful mountains．Sometimes we camp out at night．We really enjoy cooking dinner over a campfire and spending a night under the stars!

    一Sara

物质的下列用途中，是根据物质的物理性质确定的是( )

太阳半径大约是696 000千米，用科学记数法表示为____ 米．

利用计算器计算

$\sqrt{5^2-4^2}$=____ 

$\sqrt{{55}^2-{44}^2}$=____ 

$\sqrt{{555}^2-{444}^2}$=____ 

$\sqrt{{5555}^2-{4444}^2}$=____ 

仔细观察上面几道题的计算结果，试猜想$\sqrt{5··5^2-4··4^2}$=____ （100个5，100个4）