Student or Learner
1.I don't know when I can put "s" on hundred,thousand?
2.There are some mistakes on my quizzes,but I don't know why.
1.Even if I live to be "a hundred"....Never in "a million" years..why put" a"
2.It cost "thousands"....why put "s".
When you talk about exact numbers, you do not use plural (no -s): a hundred/million people, two hundred/million books, ten hundred/million dollars, etc.
'a' is used instead of 'one'
You can use it in plural when you mean 'a lot' a large quantity, more than just one hundred or one thousand: hundreds/millions of people...
I hope I've been helpful...