4² = 16 ⇒ √16 = 4

and 5² = 25 ⇒ √25 = 5

20 lies between 16 and 25

So √20 lies between √16 and √25

i.e. √20 lies between 4 and 5

I found an answer from www.quora.com

What two integers is the **square root of 20 between**? - Quora

Since **20 lies between** the two squares, 16, ( 4^2); and 25 ,(5^2), then its **square** **root lies between** 4 and 5. 782 views ·. View upvotes.

For more information, see What two integers is the **square root of 20 between**? - Quora

I found an answer from en.wikipedia.org

Triangular **number** - Wikipedia

A triangular number or triangle number counts objects arranged in an equilateral triangle. ... is also true, then the first equation is true for all **natural numbers**. ... The number of line segments **between** closest **pairs** of dots in the triangle can be ... **between** the two (and thus the difference of the two being the **square root** of the ...

For more information, see Triangular **number** - Wikipedia