Constructions question bank (Maths)

Give the justification of the construction also:
Construct a triangle with sides $5\, cm$,$6\, cm$,and $7\, cm$ and then another triangle whose sides are $\frac{7}{5}$ of the corresponding sides of the first triangle.

Construct an isosceles triangle whose base is $8\, cm$ and altitude is $4\, cm$. Then,construct another triangle whose sides are $1 \frac{1}{2}$ times the corresponding sides of the isosceles triangle. Also,provide the justification for the construction.