Problem: A rhombus is given with one diagonal twice the length of the other diagonal. Express the side of the rhombus in terms of K, where K is the area of the rhombus in square inches:
Answer Choices:
A. K​
B. 21​2K​
C. 31​3K​
D. 41​4K​
E. none of these is correct
Solution:
Let the diagonals be d and 2d. Then 21​d⋅2d=K or d2=K. Since s2=d2+(2d​)2=K+4K​=45K​, s=21​5K​.