Question

19. The cost of turfing a triangular field at the rate of Rs. 5 per square metre is Rs. 6720. If
the sides of the field are in the ratio 4:7:9, find the sides of the field.​

Answer 1

Answer:      40m, 70m, 90m

Step-by-step explanation:

Let say sides of triangles are  4a , 7a & 9a m

s = (4a + 7a + 9a)/2  = 10a  m

Using Hero formula

Area of Triangle = √(10a)(10a - 4a)(10a - 7a)(10a - 9a)

= √(10a)(6a)(3a)(a)

= 6a²√5

= 6a² * 2.24

= 13.44a²   m²

Cost = 5 *  13.44a² = 67.2 a²

67.2 a² = 6720

=> a² = 100

=> a = 10

Sides of field = 40 , 70 & 90 m

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Answer 2

here's the answer!

Answer:

Let say sides of triangles are  4a , 7a & 9a m

s = (4a + 7a + 9a)/2  = 10a  m

Using Hero formula

Area of Triangle = √(10a)(10a - 4a)(10a - 7a)(10a - 9a)

= √(10a)(6a)(3a)(a)

= 6a²√5

= 6a² * 2.24

= 13.44a²   m²

Cost = 5 *  13.44a² = 67.2 a²

67.2 a² = 6720

=> a² = 100

=> a = 10

Sides of field = 40 , 70 & 90 m

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Hope I helped!

bye!