Ballpark #23 — answers
August 17, 2026 · five estimation questions and their accepted values
Question 1
How deep is Lake Tanganyika, Africa's deepest lake, in meters?
1470
Question 2
What is the fastest tennis serve ever recorded, in km/h?
263
Sam Groth, 2012.
Question 3
How many rivets hold the Eiffel Tower together?
2500000
The classic figure: about 2.5 million.
Question 4
How many times does a person blink per day?
17000
Estimates run 15,000 to 20,000.
Question 5
How tall is Victoria Falls, in meters?
108
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