# CBSE Class 10-Mathematics: Chapter –12 Areas Related to Circles Part 13

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**Question 38:**

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 , the length of fencing metre

for , the length fencing

Perimeter i.e., circumference of the field

Let r be the radius of the field

Area of the field

Total cost of ploughing the field = Rs.

**Question 39:**

Find the difference between the area of regular hexagonal plot each of whose side 72m and the area of the circular swimming take in scribed in it. (Take

**Answer:**

Side of hexagonal plot Area of equilateral triangle

Area of hexagonal plot Area of triangle OAB

Area of circular region

Difference

**Question 40:**

In the given figure areas have been drawn of radius each with vertices A, B, C and D of quadrilateral ABCD as centers. Find the area of the shaded region.

**Answer:**

Required area Area of the circle with radius