Maths - Im so confused

There are 6 books on the shelf. The mean number of pages in the books is321. One more book is put on the shelf. The mean number of pages is now309? How many pages are in the new book?

Reply 1

Teribblestudent

Original post by D1onys1us

There are 6 books on the shelf. The mean number of pages in the books is321. One more book is put on the shelf. The mean number of pages is now309? How many pages are in the new book?

Mean = total number of pages / total number of books
321 = ? / 6
total number of pages = 321 x 6 = 1926

After adding the next book
new mean = new total pages / 7
309 = new total pages / 7
new total pages = 309 x 7 = 2163

pages added = 2163 - 1926 = 237