2. Area of a triangle = 1/2 * Base * Height
3. Area of a trapezium = 1/2 * [Sum of parallel sides] * Height
4. Area of a rhombus = 1/2 * Product of diagonals
(ii) a cube = 6a^{2}
(iii) a cylinder = 2πr(r + h)
(i) cuboid = l * b * h
(ii) cube = l^{3}
(iii) cylinder = πr^{2}h
Note:
I. All angles of a regular polygon have equal degree measures.
II. All sides of a regular polygon are equal in length.
Q1. The length and breadth of a rectangle are 10 cm and 8 cm respectively. Find its perimeter if the length and breadth are (i) doubled (ii) halved..
Ans:
Length of the rectangle = 10 cm
Breadth of the rectangle = 8 cm
(i) When they are doubled,
l = 10 × 2 = 20 cm
and b = 8 × 2 = 16 cm
Perimeter = 2(l + b) = 2(20 + 16) = 2 × 36 = 72 cm
(ii) When they are halved,
l = 10/2 = 5 cm
b = 8/2 = 4 cm
Perimeter = 2(l + b) = 2(5 + 4) = 2 × 9 = 18 cm
79 videos408 docs31 tests

1. What are the basic formulae for calculating the area and perimeter of common shapes in mensuration? 
2. How do you calculate the volume of 3D shapes like cubes and cylinders in mensuration? 
3. What is the difference between area and volume in mensuration? 
4. How can I apply mensuration formulas in reallife situations? 
5. Are there any tips for solving mensuration problems quickly and accurately? 

Explore Courses for Class 8 exam
