The base of a parallelogram is thrice its height. If the area is $867$ sq. cm, find the base of the parallelogram.

The correct option is B: $51cm$

Let height of the parallelogram be ${}^{\prime }{h}^{\prime }$ cm.

Then, the base of the parallelogram $=3h$ cm

Area of the parallelogram $=base\times height$

$=3h\times h$

$\therefore 867=3h^2$ [$\because$ Area of given parallogram $=867c{m}^2$ ]

$\Rightarrow h^2=\frac{867}{3}$

$\Rightarrow h^2=289$

$\Rightarrow h=\sqrt{289}=17cm$

Then, base $=3\times 17=51cm.$