（2015•四川达州）—Excuse me， could you please tell me the way to the 　　　　？ I have had too much water.—Go along the street and you will find one.

    Air is a colorless, tasteless and invisible（看不见的）gas that is around us. An “empty” drinking glass and an “empty” room, in fact, are not really empty. Each is filled with air. When the glass is filled with water, the water pushes the air out of the glass.
    Air, as a gas, has no definite shape, but because it is matter, it takes up space and it has weight. It is easy to prove that air is something that takes up space. Stuff a piece of dry cloth（布）into the bottom of a glass so that it will not fall out when the glass is turned upside down. Push the upside down glass, holding straight up and down, into a jar of water till the glass is completely covered. When the glass is taken out of the water, the cloth is still dry. The air inside the glass shows that it takes up space and keeps the water from coming in.

按拼音写汉字

把下面的分数化成分母是10而大小不变的分数．

$\frac{2}{5}$ =____

$\frac{20}{40}$ =____