A big thank you for your the best help but unfortunatly I am too confused about this sentence that is writen in the

dictionary of cambridge or somewhere..

sentence:A large number of invitations HAS been sent.

but on the other hand I have seen this:A small number of children ARE educated at home.

Of course I really know that after (a large number of...) normally we must use a plural verb but in that sentence in the

cambridge dictionary It is used HAS !!!!!why they do not used HAVE??????

Thanks in advance.

The truthful answer is, you can actually use both, but only sometimes. In this case, you can.

"A large number of invitations have been sent."
"A large number of invitations has been sent."

They both look correct, right?

Hope I helped!
Travis

Yep, Travis is right. The word number can be singular or plural. Go with what sounds best for you.