Class 6 Maths Chapter 9 Important Question Answers - Mensuration

Q1: The length of rectangle is thrice its breadth and its perimeter is 48cm. Find length and breadth of rectangle.
Ans: Let the breadth of rectangle = b
length of rectangle = 3b
Perimeter of rectangle = 2 × (3b + b)
48 = 2 × (3b + b)
48/2 = 4b
24 = 4b
24/4 = b
⇒ 6 = b
breadth = 6cm
length = 3b = 3 × b = 18cm.

Q2: Find the perimeter of the following figure given below.
Ans: Full-filled squares = 2
half-filled squares = 4
Area covered by full squares = 2 × 1 sq unit = 2 sq units
Area covered by half squares = 4 × 1/2 sq unit = 2 sq units
∴ Total Area = 2 sq units + 2 sq units = 4 sq units.

Q3: Find the perimeter of each of the following figures given below?
Ans: i. Perimeter = 3 cm + 3 cm + 3 cm + 3 cm + 3 cm = 15 cm
ii. Perimeter = 1 cm + 4 cm + 0.5 cm + 2.5 cm + 2.5 cm + 0.5 cm + 4 cm = 15 cm
iii. Perimeter = 1 cm + 3 cm + 2 cm + 3 cm + 4 cm + 1 cm + 3 cm + 2 cm + 3 cm + 4 cm + 1 cm + 3 cm + 2cm + 3 cm + 4 cm + 1 cm + 3 cm + 2 cm + 3 cm + 4 cm = 52 cm.

Q4: Find the area of the rectangle whose side are: 3 cm and 4 cm.
Ans: Area of the rectangle = Length × Breadth = 3 × 4 cm = 12 sq cm.

Q5: Fill in the blanks:
(a) _____ is a rectangle whose all sides are equal.
(b) The amount of surface enclosed by a figure is called its ____.
(c) For fencing the plot, we need to calculate its _____.
(d) _____ is the sum of all sides.
Ans: (a) Square
(b) area
(c) Perimeter
(d) Perimeter

Q6: The area of square is 100 cm². Its side is
Ans: Area of square = l ∗ l, here area = 100 cm² so the lenght is = l = √100 length = 10 cm.

Q7: Which figure encloses more area: a square of side 2 cm; a rectangle of side 3 cm and 2 cm; An equilateral triangle of side 4 cm?
Ans: Area of square = l × l, when l = 2 cm , Area = 4 cm²
Area of rectangle = l × b, when l = 3 cm and b = 2 cm , Area = 3 × 2 = 6 cm²
Area of an equilateral triangle =(√3 – 4)a², when a = 4 cm , Area = 6.93 cm²
so, the area of eqilateral traiangle is more

Q8: The side of a square is 12 m. Its perimeter is
Ans: Perimeter of square = 4l
here length = 12 m
so, the perimeter = 4 * 12
= 48 m

Q9: Find the area of the following figure:

Ans: Full-filled squares = 2
half-filled squares = 4
Area covered by full squares = 2 x 1 sq unit = 2 sq units
Area covered by half squares = 4 × 1/2 sq unit = 2 sq units
∴ Total Area = 2 sq units + 2 sq units = 4 sq units.

Q10: Find the perimeter of the following figure?
Ans: Perimeter
= AB + BC + CD + DE + EF + FG + GH + HI + IJ + JK + KL + LA
= 1 cm + 3 cm + 3 cm + 1 cm + 3 cm + 3 cm + 1 cm + 3 cm + 3 cm + 1 cm + 3 cm + 3 cm
= 28 cm

Q11: Find the area of the rectangle whose side are: 12 m and 21 m.
Ans: Area of the rectangle = Length × Breadth = 12 m × 21 m = 252 sq m.

Q12: State True or False:
(a) For tiling a rectangular Plot, we must calculate its area.
(b) Length and breadth of a Rectangle are 1.5m and 1m. Area is 1.5m².
(c) The Perimeter of a square is 4 times the length of the side.
(d) To find the length of fencing the square playground we must find its Perimeter.
Ans: (a) True
(b) True
(c) True
(d) True

Q13: Match the following:
Ans:

Q14: The perimeter of the given figure is

Ans: Perimeter means addition of all sides.
So Perimeter of given triangle = 30 + 30 + 40 = 100 cm.

Q15: The shape of your classroom blackboard is
Ans: The shape of the blackboard in the classroom is a rectangle as the length of the blackboard is more than the breadth it.