Adjacent Sides Of Parallelogram Are 21 Cm And 28 Cm

The adjacent sides of a parallelogram are 21 cm and 28 cm. If its one diagonal is 35 cm; find the area of the parallelogram.

Answers:

First we find area of ABC.

Sides are, a = 28 cm

b = 35 cm

and c = 21 cm

S = (a + b + c)/2

= (28 + 35 + 21)/2

= 84/2 = 42 cm

= 2 ×   21 ×   7

= 294 cm2

∵   Diagonal of ∥ gm divides it into two equal parts.

∴ area of ∥ gm = 2  ×  area of  ∆ ABC

= 2 × 294

= 588 cm2