Question

The cost of fencing a circular field at the rate of 20 per metre is 4,400. The is to be ploughed at the rate of 1.20 per sq m. Find the cost of ploughing the field.

field

(0.52 0.43) 196 17.64 aq cm.​

Answer 1

ANSWER:

Given:

• Rate of fencing the circular field = Rs 20/m
• Cost of fencing the circular field = Rs 4400
• Rate of ploughing the circular field = Rs 1.20/m²

To Find:

• Cost of ploughing the circular field

Solution:

We are given that,

⇒ Rate of fencing the circular field = Rs 20/m

⇒ Cost of fencing the circular field = Rs 4400

As, fencing is related to perimeter, so we'll use formula for perimeter of a circle here.

We know that,

⇒ Perimeter of circle = 2πr

So,

⇒ Cost of fencing the circular field = Perimeter × Rate

⇒ 4,400 = 2πr × 20

⇒ πr = 4400/40

⇒ πr = 110

⇒ 22r/7 = 110 (π = 22/7)

⇒ r = 770/22

⇒ r = 35m.

So, the radius of circular field is 35m.

Now, we have,

⇒ Rate of ploughing the circular field = Rs 1.20/m²

As, ploughing is related to area, so we'll use formula for area of a circle here.

We know that,

⇒ Area of circle = πr²

So,

⇒ Cost of ploughing the circular field = Area × Rate

⇒ Cost of ploughing the circular field = πr² × 1.20

Putting π = 22/7 and r = 35,

⇒ Cost of ploughing the circular field = 22/7 × 35 × 35 × 1.2

⇒ Cost of ploughing the circular field = 22 × 5 × 35 × 1.2

⇒ Cost of ploughing the circular field = 110 × 35 × 1.2

So,

⇒ Cost of ploughing the circular field = Rs 4,620

Hence, cost of ploughing the circular field is Rs 4,620.

Answer 2

Answer:

Cost of ploughing the circular field is Rs 4620.

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