Question

BIRD BATH

A small basin placed in a garden and filled with water for birds to bathe in.
Aashrith made a bird-bath for his garden in the shape of a hollow cylinder with a
hemispherical depression at one end as shown in figure 1. Considering the thickness of
the metal sheet used as negligible, answer the following questions:
(i) The area of a circle of radius 28 cm is:
(a) 2464 cm2

(b) 352 cm2

(c) 4928 cm2

(d) 2700 cm2

(ii) The Curved surface area of a hemisphere of radius 28 cm is:
(a) 9856 cm2

(b) 19800 cm2

(c) 4928 cm2

(d) 79200 cm2
(iii) The Curved surface area of a cylinder of radius 28 cm and height 200 cm is
(a) 19140 cm2

(b) 35200 cm2

(c) 59700 cm2

(d) 382800 cm2
(iv) Help him to calculate the total square metres of surface area he needs:
(a) 6.08 m2

(b) 7 m2

(c) 5 m2

(d) 4.01 m2
(v) Find the cost of polishing, Mayank has to bear if 1 m2 area of polish cost Rs 200.
(a) Rs 1400 (b) Rs. 802 (c) Rs. 1000 (d) Rs. 1216
please gve 4 and 5 answers

Answer 1

1 c 2d 3c 4b 5b right answer

Answer 2

1) Height , h = 1.45 m

Radius , r = 30 cm = 0.3 m

Total Surface area of the bird bath = T.S.A of Cylinder

T.S.A of Cylinder = 2πr(r+h)

= 2 × 22 / 7× 0.3 (0.3 +1.45)

= 3.3 m²

As the cylinder is attached to a hemispherical depression , its area is not added.If the cylinder was attached to a base , it would have been calculated...

2)

Answer :

CSA/TSA of sphere = 2464 cm²

Volume of sphere = 821.33 cm³

Step-by-step explanation:

• Given:

Diameter of sphere = 28 cm.

• To Find:

Curved surface area of sphere

Total surface area of sphere

Volume of sphere

Now, first we will calculate radius from diameter,

⇒ Radius = Diameter/2

⇒ Radius = 28/2

⇒ Radius = 14 cm

Now, we know that,

⇒ CSA = TSA = 4πr²

⇒ CSA = TSA = 4 × 22/7 × 14 × 14

⇒ CSA = TSA = 88 × 2 × 14

⇒ CSA = TSA = 2464 cm²

Also, we know that,

⇒ Volume of sphere = 4/3 πr³

⇒ Volume of sphere = 4/3 × 22/7 × 14 × 14

⇒ Volume of sphere = 88/21 × 14 × 14

⇒ Volume of sphere = 88/3 × 2 × 14

⇒ Volume of sphere = 2464/3

⇒ Volume of sphere = 821.33 cm³

3) In a Cylinder

Radius = 21 cm

Height = 28cm

C.S.A of Cylinder 2πrh

=2×22/7×21×28

3696cm²

and T.S.A of Cylinder = 2πr(r+h)

=2×22/7×21(21+28)

=132×49

= 6468 cm²

Hope it helps