A triangular field has two equal sides of 75 m each and a third side of 90 m. What is the cost of ploughing the field at Rs 15.60 per m2?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Rs 42,120
In an isosceles triangle, the height drawn to the third side cuts that side into two equal halves at a right angle. Pythagoras' theorem then gives the height, and the area is \(\displaystyle \frac{1}{2}\times\) base \(\times\) height.
Half of the base \(=90\div2=45\) m
Height \(=\sqrt{75^2-45^2}=\sqrt{5625-2025}=\sqrt{3600}=60\) m
Area \(\displaystyle =\frac{1}{2}\times90\times60=2700\) m2
Cost \(=2700\times15.60=\) Rs 42,120
