如图，某市在“旧城改造”中计划在一块如图所示的三角形空地上种植某种草皮以美化环境，已知这种草皮每平方米a元，则购买这种草皮至少要    (    )

两个相似多边形的一组对应边分别为3cm和4cm，如果它们的周长和为84cm，那么较大多边形的周长为（　　）

阅读下面短文，根据句意或提示，在空格处填入一个适当的词，每空一词。

    Do you know Jay Chou? If you like watching "the Voice of China" this ____ /'sΛmә/, you must know him. Jay is a very popular singer in China. Jay is his ____ name and Chou is his last name. He is thirty-seven ____ old. His was *born on January 18th. He is f____ Taiwan. His favourite sport is ____, so he plays basketball every day. And his favourite ____ is blue. He can sing ____ write songs very well. Many people like ____ (listen) to his music. He is also a good teacher at the Voice of China on Zhejiang TV, because he helps his s____ a lot. Chen Zitong and Leon Lee ____ (be) two good students in his team.