The area of a parallelogram is 72 cm^2 and its altitude is twice the corresponding base. What is the length of the base?  Choose the correct choice from the following answers:
A) 1 cm  B) 3 cm  C) 6 cm  D) 4 cm  E) 2 cm

Rationale: let base = x cm height = 2 x cm area = x ã — 2 x = 2 x ^ 2 area = x ã — 2 x = 2 x ^ 2 area is given as 72 cm ^ 2 2 x ^ 2 = 72 x ^ 2 = 36 x = 6 cm answer : c
Answer: C