RD Chapter 15- Areas Related to Circles Ex-15.2 |
RD Chapter 15- Areas Related to Circles Ex-15.3 |
RD Chapter 15- Areas Related to Circles Ex-15.4 |

**Answer
1** :
Radius of a circle = 4.2 cm

**Answer
2** :

Area of a circle = 301.84 cm^{2}

Let r be the radius, then πr2 = 301.84

**Answer
3** :

Circumference of a circle = 44 cm

Let r be the radius,

then 2πr = circumference

**Answer
4** :

Let r be the radius of the circle

∴ Circumference = 2r + 16.8 cm

⇒ 2πr = 2r + 16.8

⇒ 2πr – 2r = 16.8

**Answer
5** :

Radius of the circle (r) = Length of the rope = 28 m .

Area of the place where the horse can graze

**Answer
6** :

Area of square formed by a wire =121 cm2

∴ Side of square (a) = = 11 cm Perimeter of the square = 4 x side = 4 x 11 = 44 cm

∴Circumference of the circle formed by the wire = 44cm

Let r be the radius

**Answer
7** :
Let R and r be the radii of two circles and their ratio between them circumference = 2 : 3

**Answer
8** :

Let R and r be the radii of two circles Then R + r = 140 cm …….(i)

and difference of their circumferences

**Answer
9** :

Let the radius of a circle be r.

Circumference of a circle = 2πr

Let the radii of two circles are r_{1} andr_{2} whose

values are 15 cm and 18 cm respectively.

i.e., r_{1} = 15 cmand r_{2} = 18 cm

Now, by given condition,

Circumference of circle = Circumference of first circle + Circumference of secondcircle

⇒ 2πr = 2π r_{1} + 2πr_{2 }=

⇒ r = r_{1} + r_{2}⇒ r = 15 + 18

∴ r = 33cm

Hence, required radius of a circle is 33 cm.

**Answer
10** :

Radius of first circle (r1) = 8 cm

and radius of second circle (r2) = 6 cm

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