完形填空

　Suppose you are going to Boston, and you have never visited the city before．If someone 　1　　 　you about the interesting places in this city, you 　2　　 　to get some idea of 　3　　 　you will see．But you don't have a 　4　　 　idea of where these places are or of how to find 　5　　　．

　However, 　6　　 　someone has a map of the city and 　7　　 　you the main roads and buildings, you 　8　 , “Oh, now I 　9　　 　．I can find the way with 　10　　 　trouble at all.”

　Working in maths is somewhat（有点儿）　　 　11　　 　trying to find your way 　12　　 　a new city．Perhaps 　13　　 　the words may tell you some things and you have 　14　　 　them, but you can't see any clear road 　15　 the answers．Maybe you 　16　　 　a kind of map of the main roads in maths 　17　　 　find your way．Explore（探究）what goes on in maths, and 　18　　 　to find the main roads．They will 　19　　 　you to answers．If you can find the 　20　　 　, the maths problems can be easily worked out．