A bookseller sells 15 books in January, 16 in February and a certain number of books in March. If the average number of books he sold per month across all three months is 16, how many books did he sell in March?
##Solution## He sold an average of 16 books per month across all 3 months so he must have sold a total of 3*16 = <<16*3=48>>48 books in those 3 months
He sold 15+16 = <<15+16=31>>31 in January and February
He must have sold 48-31 = <<48-31=17>>17 books in March
#### 17