The cost of levelling the ground in the

True

Let sides of a triangle be $a=51 \mathrm{~m} b=37$ mand $c=20 \mathrm{~m}$ Now, semi-perimeter of triangle,

$s=\frac{a+b+c}{2}=\frac{51+37+20}{2}=\frac{108}{2}=54 \mathrm{~m}$

$\therefore \quad$ Area of a triangle $=\sqrt{s(s-a)(s-b)(s-c)}$   [by Heron's formula]

$=\sqrt{54(54-51)(54-37)(54-20)}$

$=\sqrt{54 \times 3 \times 17 \times 34}$

$=\sqrt{9 \times 3 \times 2 \times 3 \times 17 \times 17 \times 2}$

$=3 \times 3 \times 2 \times 17=306 \mathrm{~m}^{2}$

$\because$ Cost of levelling per $m^{2}=₹ 3$

$\therefore$ Cost of levelling per $306 \mathrm{~m}^{2}=3 \times 306=₹ 918$