How many unstressed letters in apparatus?

Here's how to figure out the unstressed letters in "apparatus":

* Break down the syllables: "ap-pa-ra-tus"

* Identify the stressed syllables: The stress falls on the second syllable: "ap-pa-ra-tus"

* Count the letters in the unstressed syllables: There are two unstressed syllables: "ap" and "tus"

* Count the letters in those syllables: "ap" has 2 letters, and "tus" has 3 letters.

Therefore, there are 5 unstressed letters in "apparatus."