A triangular field has two equal sides of 50 m each and a third side of 80 m. What is the cost of levelling the field at Rs 8.50 per m2?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Rs 10,200
In an isosceles triangle the height to the unequal side meets it at its middle, so the height comes from Pythagoras. Then area \(=\frac{1}{2}\times\) base \(\times\) height, and cost \(=\) area \(\times\) rate.
Half of the base \(=80\div2=40\) m
Height \(=\sqrt{50^2-40^2}=\sqrt{2500-1600}=\sqrt{900}=30\) m
Area \(=\displaystyle\frac{1}{2}\times80\times30=1200\) m2
Cost \(=1200\times8.50=\) Rs 10,200
