To locate √10 on number line follow the steps.let 3cm = 1 unit
1] √10 = √3²+1²
2]draw a number line OC such that OA=AB=OC=1 unit
3] draw a perpendicular line from C of 1 unit [as √10 = √3²+ ] and name the point as C
4] join O and C  it will form a triangle 
       by pythagoras theorem  
           OC = √10
           now taking the radius of OC in compass draw an arc touching the number line . 
and that point will be   √10 .
Zyan you did a mistake! In the first step root 10 =root 9 square+1 square
i know that but i was telling him to just locate . what u r talking abt is spiral method ..
Draw a 3unit line and a perpendicular line of 1unit and then hypotenuse isroot 10