Find the area of a rhombus one side of which measures 20 cm and one diagonal is 28 cm.  Choose the correct option:
A) 200 cm 2 B) 300 cm 2 C) 400 cm 2 D) 448 cm 2 E) 100 cm 2

Rationale: explanation : let other diagonal = 2 x cm . since diagonals of a rhombus bisect each other at right angles , we have : ( 20 ) 2 = ( 12 ) 2 + ( x ) 2 = > x = √ ( 20 ) 2 – ( 12 ) 2 = √ 256 = 16 cm . _ i so , other diagonal = 32 cm . area of rhombus = ( 1 / 2 ) x ( product of diagonals ) = ( 1 / 2 × 28 x 32 ) cm 2 = 448 cm 2 answer : option d
Answer: D