We counted to 39 in ASL, let's keep going!
To do the sign for 40, make the hand sign for 4 with your thumb tucked in and your four fingers pointed up.
Then close your fingers together all pointed forward away from you, for zero.
For 41 through 49, just do the sign for 4, and then the sign for the number 1-9.
Here is a helpful video to show how these signs are done.
ASL Numbers 30-100 in Sign Language - My Smart Hands
(from: wikipedia - american sign language)
Italian: quaranta, quarantuno, quarantadue, quarantatre, quarantaquattro, quarantacinque, quarantasei, quarantasette, quarantotto, quarantanove
German: vierzig, einundvierzig, zweiundvierzig, dreiundvierzig, vierundvierzig, fünfundvierzig, sechsundvierzig, siebenundvierzig, achtundvierzig, neunundvierzig
Spanish: quarenta, quarenta y uno, quarenta y dos, quarenta y tres, quarenta y cuatro, quarenta y cinco, quarenta y seis, quarenta y siete, quarenta y ocho, quarenta y nueve
French: quarante, quarante et un, quarante-deux, quarante-trois, quarante-quatre, quarante-cinq, quarante-six, quarante-sept, quarante-huit, quarante-neuf