Find the area of a rhombus one side of which measures 20 cm and one diagonal is 25 cm.  Choose the correct choice from the following answers.
A) 700 cm 2
B) 600 cm 2
C) 500 cm 2
D) 400 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 × 25 x 32 ) cm 2 = 400 cm 2 answer : option d"
Answer: D