In this page curved surface area solution9 we are going to see solution of some practice questions.

**Question 19**

Find the curved surface area and total surface of a hollow hemisphere whose outer and inner radii are 4.2 cm and 2.1 cm respectively.

**Solution:**

Inner radius (r) = 2.1 cm

Outer radius (R) = 4.2 cm

Curved surface area = 2Π (R² + r²)

= 2 **x** Π** x** [(4.2)² + (2.1)²]

= 2 **x** Π** x** (17.64 + 4.41)

= 2 **x** Π** x** (22.05)

= 44.1 Π cm²

Total surface area = 2Π (R² + r²) + Π (R² - r²)

= 44.1 Π + Π** x** [(4.2)² - (2.1)²]

= 44.1 Π + Π (17.64 - 4.41)

= 44.1 Π + Π (13.23)

= 44.1 Π + 13.23 Π

= 57.33 Π cm²

**Curved surface area = 44.1 Π cm² **

**Total surface area = 57.33 Π cm² **

**Question 20**

The inner curved surface area of a hemisphere dome of a building needs to be painted . If the circumference of the base is 17.6 m,find the cost of painting it at the rate of $5 per sq.m

**Solution:**

Circumference of the base = 17.6 m

2 Π r = 17.6

2 **x** (22/7) **x** r = 17.6

r = 17.6 **x **(1/2) **x **(7/22)

r = 2.8 m

Curved surface area of hemisphere = 2 Π r²

= 2 **x **(22/7) **x **(2.8)²

= 49.28 m²

Cost of painting $ 5 per square meter

Total cost = 5 **x** 49.28

= $ 246.40

Outer radius (R) = 4.2 cm

curved surface area solution9 curved surface area solution9

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- Area
- Curved Surface Area
- Total Surface Area
- Volume
- Cylinder
- Conoid (Cone)
- Sphere
- Problems on Curved Surface Area
- Problems on Total Surface Area
- Problems on Volume
- Formulas For Shapes
- Perimeter of Sector
- Perimeter of Sector Worksheets
- Length of Arc
- Practice questions on length of arc
- Perimeter of square
- Perimeter of Parallelogram
- Perimeter of Rectangle
- Perimeter of a Triangle
- Area of a Circle
- Area of Semicircle
- Area of Quadrant
- Area of a Sector
- Area of a Triangle
- Area of Equilateral Triangle
- Area of Scalene Triangle
- Area of Square
- Area of Rectangle
- Area of Parallelogram
- Area of Rhombus
- Area of Trapezium
- Area of Quadrilateral
- Area Around Circle
- Path Ways
- Combined Figures