Ballpark #42 — answers
September 5, 2026 · five estimation questions and their accepted values
Question 1
How long is the Rhine River, in kilometers?
1230
Question 2
How many colors can the human eye distinguish, in millions?
10
The classic estimate is about 10 million.
Question 3
What is the population of Iceland, in thousands?
390
Question 4
How much does a blue whale’s tongue weigh, in kilograms?
2700
Roughly the weight of an elephant.
Question 5
How many minutes does the International Space Station take to orbit Earth once?
90
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