Area & Perimeter NCERT Exercise 11.2
Question 1: Find the area of each of the following parallelograms:
(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
(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
(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.
(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. | Base | Height | Area of Parallelogram |
|---|---|---|---|
| (a) | 20 cm | 246 sq cm | |
| (b) | 15 cm | 154.5 sq cm | |
| (c) | 8.4 cm | 48.72 sq cm | |
| (d) | 15.6 cm | 16.38 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. | Base | Height | Area of triangle |
|---|---|---|---|
| (a) | 15 cm | 87 sq cm | |
| (b) | 31.4 mm | 1256 sq mm | |
| (c) | 22 cm | 170.5 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