According to the Pythagoras theorem, we can conclude that
( √5 )2 = ( 2 )2 + ( 1 )2.
We need to draw a line segment AB of 1 unit on the number line. Then draw a straight line segment BC of 2 units. Then join the points C and A, to form a line segment BC.
Then draw the arc ACD, to get the number √5 on the number line.