DPI of a PDA screen

Background:

Pixels-per-inch, also dots-per-inch or DPI, is a measure of the resolution of a computer screen, in terms of how many pixels can be fitted along a horizontal or vertical line of the screen one inch in length. The higher the DPI, the smaller the pixels will be. PC screens are typically considered to be 96 DPI.

Question:

My palmtop’s screen is 480×160 pixels and measures 4.75" diagonally, as shown in the illustration. Given this information, What is its resolution in pixels-per-inch? To help you with the question, a variable x has been introduced.

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