Question

Estimate: √20
A. 4
B. 5
C. 6
D. 7

Answer 1

a<b<c
b is the square root of 20
if we square everybody
a²<b²<c²
if we say that b²=20 then

a²<20<c²
find a and c

2^2=4
3^2=9
4^2=16
5^2=25

16<20<25
sqrt both sides
4<√20<5

somewhere between 4 and 5
closer to 16 than 25

A

Answer 2

$\sqrt{20}=\sqrt{4*5}=2 \sqrt{5}$
$\sqrt{5}$ is around 2, and 2 * 2 = 4, so the estimate is about 4.