Here's why:
* Short vowel sounds are typically found in words where the vowel is followed by one or two consonants. In "cake," the vowel "a" is followed by the consonants "k" and "e."
* Long vowel sounds are often found in words where the vowel is followed by a single consonant and a silent "e" at the end of the word.
Since "cake" doesn't follow the pattern of a long vowel sound, it has a short "a" sound.