Please solve the programming task below using a self-contained code snippet in a markdown code block.

A sentence is a string of single-space separated words where each word can contain digits, lowercase letters, and the dollar sign '$'. A word represents a price if it is a sequence of digits preceded by a dollar sign.

For example, "$100", "$23", and "$6" represent prices while "100", "$", and "$1e5" do not.

You are given a string sentence representing a sentence and an integer discount. For each word representing a price, apply a discount of discount% on the price and update the word in the sentence. All updated prices should be represented with exactly two decimal places.
Return a string representing the modified sentence.
Note that all prices will contain at most 10 digits.
 
Please complete the following python code precisely:
```python
class Solution:
    def discountPrices(self, sentence: str, discount: int) -> str:
```