Question

Please give all the formulas from the chapter Mensuration (Class 8)

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Answer 1

✳️Some important mensuration formulas are:

❄️Area of rectangle (A) = length(l) × Breath(b)

❄️Perimeter of a rectangle (P) = 2 × (Length(l) + Breath(b))

❄️Area of a square (A) = Length (l) × Length (l)

❄️Perimeter of a square (P) = 4 × Length (l)

❄️Area of a parallelogram(A) = Length(l) × Height(h)

❄️Perimeter of a parallelogram (P) = 2 × (length(l) + Breadth(b))

❄️Area of a triangle (A) = (Base(b) × Height(b)) / 2

❄️Perimeter of a trapezium (P) = sum of all sides

❄️Area of rhombus (A) =  Product of diagonals / 2

❄️Perimeter of a rhombus (P) = 4 × l
where l = length of a side

❄️Area of quadrilateral (A) = 1/2 × Diagonal × (Sum of offsets)

Answer 2

→ Prism:

(i) Area of the lateral faces of a right prism = perimeter of the base × height.  

(ii) Area of the whole surface of a right prism = Area of the lateral faces + 2 × area of the base.  

(iii) Volume of a right prism = area of the base × height.

Perimeter and Area of Rectangle:

● The perimeter of rectangle = 2(l + b).  

● Area of rectangle = l × b; (l and b are the length and breadth of rectangle)

● Diagonal of rectangle = √(l² + b²)

Perimeter and Area of the Square:

● Perimeter of square = 4 × S.  

● Area of square = S × S.  

● Diagonal of square = S√2; (S is the side of square)  

Perimeter and Area of the Triangle:  

● Perimeter of triangle = (a + b + c); (a, b, c are 3 sides of a triangle)  

● Area of triangle = √(s(s - a) (s - b) (s - c)); (s is the semi-perimeter of triangle)  

● S = 1/2 (a + b + c)  

● Area of triangle = 1/2 × b × h; (b base , h height)  

● Area of an equilateral triangle = (a²√3)/4; (a is the side of triangle)  

Perimeter and Area of the Parallelogram:  

● Perimeter of parallelogram = 2 (sum of adjacent sides)  

● Area of parallelogram = base × height  

Perimeter and Area of the Rhombus:  

● Area of rhombus = base × height  

● Area of rhombus = 1/2 × length of one diagonal × length of other diagonal

● Perimeter of rhombus = 4 × side

Perimeter and Area of the Trapezium:  

● Area of trapezium = 1/2 (sum of parallel sides) × (perpendicular distance between them)  

                               = 1/2 (p₁ + p₂) × h (p₁, p₂ are 2 parallel sides)  

Circumference and Area of Circle:  

● Circumference of circle = 2πr

                                       = πd

                      Where, π = 3.14 or π = 22/7

                                    r is the radius of circle  

                                    d is the diameter of circle

● Area of circle = πr²

● Area of ring = Area of outer circle - Area of inner circle.

Thank u.