3rd grade math
posted by Pam & Hannah .
Double my tens digit to get my ones digit. Double me and I am less than 50. Who am I?

Here are some numbers that answer your first clue.
21, 42, 63
Which of these answers your second clue? 
Thank you. We sat and figured it out after we posted the question and we got it right. 21. But thanks for taking they time to respond to us. We are definitely bookmarking this site for future help!!

You're very welcome.
And welcome to Jiskha! 
mustery number