The Count of Things

Bluebulb Projects' The Measure of Things presents:

It's about nine-tenths the number of Countries in the European Union

In other words, 25 is 0.930 times the count of Countries in the European Union, and the count of Countries in the European Union is 1.10 times that amount.

(a.k.a. EU) (2016 figures)
There are 27 member countries in the European Union, the latest member of which is Croatia. The EU is largely urban, with over twenty cities having a population of one million or more, and 75% of the population living in an urban area.

It's about one-and-seven-tenths times the number of Living Kings and Queens

In other words, the count of Living Kings and Queens is 0.590 times 25.

(2015 figures) (distinct Monarchs)
As of 2015, the world has fifteen Kings and Queens reigning over 45 countries. Of all these, Queen Elizabeth the II is the only reigning Queen; she has monarchical authority over the sixteen of the Commonwealth nations.

It's about half the number of Teeth in a Great White Shark's Mouth

In other words, 25 is 0.520 times the count of Teeth in a Great White Shark's Mouth, and the count of Teeth in a Great White Shark's Mouth is 1.90 times that amount.

(Carcharodon carcharias) (average; including developing rows)

It's about half the number of Countries in Africa

In other words, 25 is 0.450 times the count of Countries in Africa, and the count of Countries in Africa is 2.20 times that amount.

(2016 figures) (sovereign states recognized by the UN only)

It's about three times the number of Symphonies Composed by Beethoven

In other words, 25 is 2.777777777780 times the count of Symphonies Composed by Beethoven, and the count of Symphonies Composed by Beethoven is 0.360 times that amount.

(a.k.a. Ludwig van Beethoven)

It's about one-third the number of Submarines in the US Navy

In other words, the count of Submarines in the US Navy is 2.90 times 25.

(a.k.a. Subs) (includes all types, all classes) (2015 figures)
The United States Navy maintains a fleet of 72 active submarines. A typical submarine goes to sea with a crew of about 140.

It's about three-tenths the number of Keys on a Piano

In other words, 25 is 0.280 times the count of Keys on a Piano, and the count of Keys on a Piano is 3.60 times that amount.

(Moden layout; A₀ to C₇)