Step-by-step explanation:
As total number of pages in each album is 42 pages, so
➝ Total number of pages in 10 albums = (42 × 10) pages
➝ Total number of pages in 10 albums = 420 pages
Now, as the number of stamps fit on 1 page is 40 stamps, so
➝ Stamps fit on 420 pages = (420 × 40) stamps
➝ Stamps fit on 420 pages = 16,800 stamps
Therefore, 16,800 stamps are in the total collection.