题干

在学习掷硬币的概率时,老师说:“掷一枚质地均匀的硬币,正面朝上的概率是 ”,小明做了下列三个模拟实验来验证.

①取一枚新硬币,在桌面上进行抛掷,计算正面朝上的次数与总次数的比值;

②把一个质地均匀的圆形转盘平均分成偶数份,并依次标上奇数和偶数,转动转盘,计算指针落在奇数区域的次数与总次数的比值;

③将一个圆形纸板放在水平的桌面上,纸板正中间放一个圆锥(如图),从圆锥的正上方往下撒米粒,计算其中一半纸板上的米粒数与纸板上总米粒数的比值. 上面的实验中,不科学的有(  ).

A:0个

B:1个

C:2个

D:3个

上一题 下一题 0.0难度 选择题 更新时间:2016-03-02 12:06:30

答案(点此获取答案解析)

A

同类题4

阅读下列短文,从每小题所给的A、B、C、D四个选项中选出一个最佳选项。

    Sarasota, Florida teen band The Garbage-Men is performing on the stage. The band has five members. They are Jack Berry, Ollie Gray, Harrison Paparatto, Austin Siegel and Evan Tucker. The five teens are making music from waste. The Garbage-Men band's instruments are made from recycled things. The guitars are boxes. A horn(号) is made from pipes. The keyboard is formed from old bottles.

    The band started about two years ago. Jack Berry who was in eighth grade at the time decided to make a playable, home-made guitar, after some trial-and-error(反复试验), he ended up building it from a cereal box, a yardstick and toothpicks. After Jack showed his creation to his friend Ollie Gray, Ollie had the idea to form a band using other home-made instruments as a way to improve recycling. “We want to show people there is more to recycling than throwing things away in the bin.” Jack, 16, told TFK. “You can actually reuse materials.”

    The Garbage-Men plays at local events around Sarasota, including festivals, farmer's markets and community fundraisers. Typically, the teens will set up on the street and perform popular songs from the 1960s, including classic Beatles tunes and crowd favorite “Wipe Out,” by The Surfaris. In between sets, they talk about recycling and offer tips for how to help the environment. While they perform, Jack's little brother Trent, 11, gives out flyers(宣传单) about recycling and helps sell the band's CDs and other musical products.

    The band donates(捐赠) the money from sales to charity. They have raised more than $2,500 for Heifer International. The organization gives farm animals, seeds and agricultural(农业的) training to people in poor countries to help end poverty and hunger. “It's a good, sustainable-development (持续发展的)charity,” Jack says, “By donating one animal, you help the whole community.”

    The band, all tenth graders, tries to play a show every week. They've also played on a Tampa, Florida radio station and auditioned(试演) for America's Got Talent. The teens hope to eventually take their shows on the road by touring in other states. “Music is a really good way to get a good message across to people because it's really accessible(可接近的),” Jack says. Their instruments may be rubbish, but their message isn't.