**Formula's:**

__Area__of FULL circle =**π**× r x r

Area of semi-circle = (

**π x r x r) / 2**

__Circumference__of FULL circle = 2πr**Circumference of semi-circle = (2**

**πr) / 2**

**1.**

**The radius of the smaller circle is 3.5 cm. The radius of the larger circle is twice that of the smaller circle. Find the area of: (pi = 22/7)**

**i.) The big circle**

**ii.) The small circle**

**iii.) The shaded part**

i. 22/7 x 7 x 7

154 cm2

ii. 22/7 x 3.5 x 3.5

= 38.5 cm2

iii. Area big circle - area small circle

= 154 - 38.5

= 115.5 cm2

154 cm2

ii. 22/7 x 3.5 x 3.5

= 38.5 cm2

iii. Area big circle - area small circle

= 154 - 38.5

= 115.5 cm2

**2.**

**A swimming has the shape of a semi-circle. If the straight side (diameter) is 14 meters, find the perimeter of the pool. [pi=(22/7)]**

C = 2πr

= 2 x 22/7 x 7

= 44cm

= 44 x 1/2 (semi circle)

= 22cm

22 + 14 = 36cm (remember to add the straight side)

= 2 x 22/7 x 7

= 44cm

= 44 x 1/2 (semi circle)

= 22cm

22 + 14 = 36cm (remember to add the straight side)

**3.****The sides of the square piece of paper is 22 cm long. If a semi-circle was cut on one side, what is the area of the remaining piece of paper? [ pi = (22/7) ]**

Area of square:

l x b = 22 x 22 = 484 cm2

Area semicircle:

22/7 x 11 x 11 = 380.26

380.26 x 1/2 = 190.13 cm2

Area square - area semi circle:

484 - 190.13 = 293.87 cm2

l x b = 22 x 22 = 484 cm2

Area semicircle:

22/7 x 11 x 11 = 380.26

380.26 x 1/2 = 190.13 cm2

Area square - area semi circle:

484 - 190.13 = 293.87 cm2

**4.**

**The rectangle has length 20 cm and breadth 7 cm. Find the area of the shaded portion? [ pi = (22/7) ]**

Area rectangle:

l x b = 20 x 7 = 140 cm2

Area circle:

22/7 x 3.5 x 3.5

= 38.5 cm2

Area rectangle - area circle:

140 - 38.5 = 101.5 cm2

l x b = 20 x 7 = 140 cm2

Area circle:

22/7 x 3.5 x 3.5

= 38.5 cm2

Area rectangle - area circle:

140 - 38.5 = 101.5 cm2

**5.**

**C is the centre of the larger semi-circle. The smaller semi-circle has a radius of 3 m. Find the**

__perimeter__of the shape shown in the diagram. (pi = 3.14)Perimeter (circumference) of larger semi circle:

2 x 3.14 x 6

= 37.68 cm

Perimeter (circumference) of smaller semi circle:

2 x 3.14 x 3

= 18.84 cm

Total perimeter = circumference of larger semicircle + circumference of smaller semicircle + the straight line to C.

= 37.68 + 18.84 + 6

= 62.52cm

2 x 3.14 x 6

= 37.68 cm

Perimeter (circumference) of smaller semi circle:

2 x 3.14 x 3

= 18.84 cm

Total perimeter = circumference of larger semicircle + circumference of smaller semicircle + the straight line to C.

= 37.68 + 18.84 + 6

= 62.52cm