There are many students reading books in the library, 40% of them are boys, and then four boys come in. At this time, boys accounted for 65438+7/06 of the total number. How old is the library?
Solution: There are X people in the library. The meaning of the question shows that:
0.4x+4=7/ 16(x+4)
7/ 16x-0.4x=9/4
35/80x=9/4
x=60
There are 60 people in the library.
There are 60 people in the library.