# CBSE Class 10-Mathematics: Chapter –12 Areas Related to Circles Part 15

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Question 46:

The radii of two circles are 19cm and 9cm, respectively. Find the radius of the circle which has its circumference equal to the sum of the circumference of the two circles

Answer:

circumference of the 1st circle

circumference of the 2nd circle

Question 47:

A car travels distance in which each wheel makes complete revolutions. Find the radius of its wheel

Answer:

Distance travelled by a wheel in complete revolutions

Distance travelled in one revolution

Let r be the radius of the wheel

Question 48:

A sector is cut from a circle of diameter . If the angle of the sector is 1500 find its area.

Answer:

We have,

Diameter

Angle of sector

Area of the sector

Question 49:

In the given figure AOBCA represent a quadrant of area . Calculate the area of the shaded portion.

Answer:

Required area = Area of quadrant OAB – Area of

## 3 Mark Questions

Question 1:

The cost of fencing a circular field at the rate of per metre is . The field is to be ploughed at the rate of . Find the cost of ploughing the field.

Answer:

Since for Rs. , the length of fencing 1metre

for Rs , the length of fencing

Perimeter i.e. circumference of the field

Let r be radius of the field.

Area of the field

Total cost of ploughing the field