Get rid of the "3" in triplets

A lot of times in sheet music, you only need to put the "3" above the first couple of triplets; after that it is understood that they are triplets and you no longer need to label the groups of three notes with a "3." Is it possible to do this? I got like two pages of music with triplets with a "3" above the triplets, but when I select the "3" only by clicking on it and then cut or delete, it deletes all the notes. I guess I can live with all the "3s" but it is not very professional.