The GATE Grind

GATE 2023 CE (CE1) – Question 23

Geomatics Engineering · Maps, scale, coordinate systems, cartography and map projections · 1 mark · Multiple choice

A student is scanning his 10 inch × 10 inch certificate at 600 dots per inch (dpi) to convert it to raster. What is the percentage reduction in number of pixels if the same certificate is scanned at 300 dpi?

  1. 62
  2. 88
  3. 75
  4. 50

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Correct answer: (C) 75

Explanation

The number of pixels is proportional to the square of the resolution. At 300 dpi it is $\left(\frac{300}{600}\right)^2 = \frac{1}{4}$ of that at 600 dpi, a reduction of 75%.