已知两个非零向量a与b，定义|a×b|＝|a|·|b|sin θ，其中θ为a与b的夹角．若a＝(－3,4)，b＝(0,2)，则|a×b|的值为________．

单句改错（共5小题，每小题1分，满分5分）

每句只有一个错误。按下列情况改正：该句多一个词，把多余的词用斜线（\）划掉，在该行右边横线上写出该词，并也用斜线划掉；该句缺一个词，在缺词处加一个漏字符号（∧），在该句右边横线上写出该加的词；该句错一个词，在错的词下划一横线，在该句右边横线上写出改正后的词。

注意：不要改动原句的意思。

1. Little Mary felt cold, so she stood closely to her mother.                                   

2. There are a huge number of workers are striking in the street for better working conditions.       

3. Please put the book to where it was, so that we can easily find it.                           

4. One of the world’s largest art galleries, the Louvre, located in Paris.                           

5. I would gladly pay twice as many for the book, because it is quite a useful one.