In what way similarity of triangles is different from similarity of other polygon?

All squares are 

Squares of all sizes are similar.

All squares are similar

On a map drawn to a scale of $1:50000$, a rectangular plot of land $ABCD$ has dimensions $AB=6cm,BC=8cm$, and all angles are right angles. 

(i) the actual length of the diagonal distance  $AC$ of the plot in $km.$

(ii) the actual area of the plot in sq km.

$3$ squares are represented in the following three figures. For this figure, _____statement is true.

Fill in the blank using the correct word given in the bracket.

All circles are _____ (Congruent, similar)

A model of a high rise building is made to a scale of $1 : 50$. If the floor area of a flat in the building is $20 m^2$, find the floor area of that in the model.

The model of a building is constructed with the scale factor $1 : 30$.

If the actual volume of a tank at the top of the building is $27 m$, find the volume of the tank on the top of the model.

What are congruent circles?