A few years ago, Dave Stirling had the idea of selling CDs over the Internet. The business he started from his home in Ohio, the USA, now sells 500,000 CDs a year and has made him into a millionaire(百万富翁)at the age of 24.
"I could see that this was the future of shopping," says Stirling. "Why should you pay $15 for a CD and spend the time and the money getting into the store and parking your car? You can have the same CD for half of the price by clicking(敲击)on your computer. And we can find any CD you want and bring it to your door in 24 hours!"
According to Stirling, this is the only beginning, "I believe that one day we'll do our shopping over the net: it's easier, quicker and cheaper. Shops and supermarkets will be the past."

在平面上，$\overrightarrow{A{B}_1}$⊥$\overrightarrow{A{B}_2}$，|$\overrightarrow{O{B}_1}$|=|$\overrightarrow{O{B}_2}$|=1，$\overrightarrow{OP}$=$\overrightarrow{A{B}_1}$+$\overrightarrow{A{B}_2}$．若|$\overrightarrow{AP}$|＜$\frac{1}{3}$，则|$\overrightarrow{OA}$|的取值范围是____ 

某校九年级历史兴趣小组在开展研究性学习时收集了希波战争、布匿战争、马可•波罗来华等素材，这些素材反映的共同主题是（    ）

把10克盐溶于40克水中，盐占盐水的____%。