A Boy Read 4/5th Of Story Book Which Has 500 Pages Numbered 1,2,3, And So On. How Man…

a boy read 4/5th of story book which has 500 pages numbered 1,2,3, and so on. how many pages remains

If a boy has read the 4/5 of the book consider that it contains 50 pages. Let 1=100, 2=200, 3=300, 4=400 and 5=500. So the pages remain unread is only 100.