Find the lenghth of AB sides of ABCD parallelogram AD = (3/5)AB . Perimeter of ABCD is 11.2 cm .

If ABCD is a parallelogram, it's opposite sides are equal and parallel.

AB=CD and AD=BC

From the enunciation we'll have:

AD=(3/5)AB

We'll calclualte the perimeter of the parallelogram:

P=2AB+2AD=2(AB+AD)=2[AB+(3/5)AB]

We'll substitute in the formula of perimeter all we know:

11.2 = 2[AB+(3/5)AB]

5.6 = AB+(3/5)AB

We notice that we'll have to have the same denominator, both sides of equality, the denominator being 5.

5*5.6 = 5*AB + 3*AB

28 = 8AB

AB=7/2cm

AB=3.5cm

AD= (3/5)AB

AD= (3/5)*3.5

AD=2.1cm