Area & Perimeter

Exercise 11.2

Question 1: Find the area of each of the following parallelograms:

parallelogram parallelogram

(a) Given, Base = 7cm and Height = 4cm

We know that Area of parallelogram = Base `xx` Height

Therefore, Area of the given parallelogram `= 7 cm xx 4 cm = 28` cm2

(b) Given, Base of the given parallelogram = 5cm and height = 3 cm

Therefore, area of the given parallelogram = Base `xx` Height

`= 5 cm xx 3 cm = 15` cm2


parallelogram parallelogram

(c) Given, Base of the given parallelogram = 2.5cm and height = 3.5 cm

Therefore, area of the given parallelogram = Base `xx` Height

`= 2.5 cm xx 3.5 cm = 8.75` cm2

(d) Given, Base of the given parallelogram = 5cm and height = 4.8 cm

Therefore, area of the given parallelogram = Base `xx` Height

`= 5 cm xx 4.8 cm = 24` cm2

parallelogram

(e) Given, Base of the given parallelogram = 2cm and height = 4.4 cm

Therefore, area of the given parallelogram = Base `xx` Height

`= 2 cm xx 4.4 cm = 8.8` cm2


Question 2: Find the area of each of the following triangles.

triangles

(a) Given; base = 4 cm and height = 3 cm

Area of triangle `= 1/2 xx \text(base) xx\ text(height)`

`= 1/2 xx 4 xx 3 = 6` sq cm

(b) Given; base = 5 cm and height = 3.2 cm

Area of triangle `= 1/2 xx \text(base)xx\text(height)`

`= 1/2 xx 5 xx 3.2 = 8` sq cm

(c) Given; base = 3 cm and height = 4 cm

Area of triangle `= 1/2 xx\text(base)xx\text(height)`

`= 1/2 xx 3 xx 4 = 6` sq cm

(d) Given; base = 3 cm and height = 2 cm

Area of triangle `= 1/2xx\text(base)xx\text(height)`

`= 1/2 xx 3 xx 2 = 3` sq cm

Question 3: Find the missing values.

S. No.BaseHeightArea of Parallelogram
(a)20 cm246 sq cm
(b)15 cm154.5 sq cm
(c)8.4 cm48.72 sq cm
(d)15.6 cm16.38 sq cm

(a) Given: Base = 20 cm, Area = 246 cm2

Area = Base `xx` Height

`⇒246  cm^2= 20 cm \xx\ text(Height)`

Or, `text(height) = (246)/(20) = 12.3` cm

(b) Given, Height = 15 cm, Area = 154.5 cm2, Base = ?

Area = Base `xx` Height

`⇒154.5 cm^2 = text(Base) xx 15 cm`

Or, base `= (154.5)/(15) = 10.3` cm

(c) Given, Height = 8.4 cm, Area = 48.72 cm2, Base = ?

Area = Base `xx` Height

`⇒48.72 cm^2 = text(Base) xx 8.4 cm`

Or, base `= (48.72)/(8.4) = 5.8` cm

(d) Given: Base = 15.6 cm, Area = 16.38 cm2

Area = Base `xx` Height

`⇒ 16.38 cm^2 = 15.6 cm xx \text(Height)`

Or, height `= (16.38)/(15.6) = 1.05` cm


Question 4: Find the missing values.

S. No.BaseHeightArea of triangle
(a)15 cm87 sq cm
(b)31.4 mm1256 sq mm
(c)22 cm170.5 sq cm

(a) Given, Base = 15cm, Area of triangle = 87 cm2, Height = ?

Area of triangle `= 1/2 xx \text(Base) xx \text(Height)`

Or, `87 = 1/2 xx 15 xx \text(Height)`

Or, Height `= (87 xx 2)/(15) = 11.6` cm

(b) Given, Height = 31.4 mm, Area of triangle = 1256 mm2, Base = ?

Area of triangle `= 1/2 xx \text(Base) xx \text(Height)`

Or, `1256 = 1/2 xx \text(Base) xx 31.4`

Or, Base `= (1256 xx 2)/(31.4) = 80` mm

(c) Given, Base = 22cm, Area of triangle = 170.5 cm2, Height = ?

Area of triangle `= 1/2 xx \text(Base) xx \text(Height)`

Or, `170.5 = 1/2 xx 22 xx \text(Height)`

Or, Height `= (170.5 xx 2)/(22) = 15.5` cm



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