Estimation question

How many X-Rays are done in the World in a Year?

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What this question tests

Estimation using population health data and typical medical imaging frequency across countries.

Pick a method: top-down from world population and average X-ray frequency per person per year.
Segment by country income level, since developed countries have far higher access to imaging than low income countries.
Assume a rough split: roughly 20 percent of world population in high access regions averaging 0.5 X-rays a year, and the rest averaging much lower, closer to 0.1.
Include dental X-rays as a large separate contributor, since they are far more frequent than medical imaging X-rays.
Multiply each segment's population by its assumed frequency and sum for a global total.
State the result as an order of magnitude, likely in the low billions annually, not a precise figure.

Segments the world population by healthcare access level rather than applying one global average.
Separately accounts for dental X-rays, which are far more common than diagnostic medical X-rays and easy to overlook.
States clear numeric assumptions for each segment's frequency, marked openly as estimates.
Lands on an order of magnitude, low billions per year, with the reasoning visible.

Applying a single developed-world frequency assumption to the entire global population.
Forgetting dental and veterinary X-rays, which are a large share of total imaging.

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