Explanation: Numbers 16-19 have special forms. Diecisiete = diez (10) + siete (7). Note it's written as one word, not "diez y siete."
Explanation: Numbers above 30 use "y" (and) between tens and ones. 35 = treinta (30) y (and) cinco (5).
Explanation: For times after 1:00, use "son las" + number. 3:00 = "Son las tres" (They are the three o'clock).
Explanation: 1:00 is singular, so use "es la una" (it is the one o'clock). Only 1:00 is singular; all other times use "son las."
Explanation: 91 = noventa (90) y (and) uno (1). Always use "y" between tens and ones.
Explanation: For 30 minutes, use "y media" (and half), not "y treinta." 4:30 = "Son las cuatro y media."
Explanation: For 15 minutes, use "y cuarto" (and quarter). 5:15 = "Son las cinco y cuarto."
Explanation: 100 is "cien." When followed by another number (like 101), it becomes "ciento," but 100 alone is "cien."