Ex.11.2 Q2 Perimeter and Area - NCERT Maths Class 7

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Question

Find the area of each of the following triangles:

Text Solution

What is known?

Base and height of triangles.

What is the unknown?

The area of the triangles.

How can you use the known information to arrive at the solution?

Base and height of a triangle is already given. Area of triangle is equal to half of product of base and height.

Steps:

(a) Given,

Base \(= 3 \,\rm cm\)

Height \(= 4 \,\rm cm\)

We know that

\(\begin{align}&\text{Area of triangle} \\ &= \frac{1}{2} \times {\rm{Base}} \times {\rm{Height}} \end{align}\)

\(\begin{align}&= \frac{1}{2} \times {\rm{3}} \times {\rm{4}}\\&= {\rm{6}}\;{\rm{c}}{{\rm{m}}^2}\end{align}\)

(b) Given

Base \(= 5 \,\rm cm\)

Height \(= 3.2 \,\rm cm\)

\(\begin{align}&\text{Area of triangle} \\ &= \frac{1}{2} \times {\rm{Base}} \times {\rm{Height}} \end{align}\)

\(\begin{align} &= \frac{1}{2} \times {\rm{5}} \times {\rm{3}}{\rm{.2}}\\&= {\rm{8}}\;{\rm{c}}{{\rm{m}}^2}\end{align}\)

(c) Given

Base \(= 3 \,\rm cm\)

Height \(= 4 \,\rm cm\)

\(\begin{align}&\text{Area of triangle} \\ &= \frac{1}{2} \times {\rm{Base}} \times {\rm{Height}} \end{align}\)

\(\begin{align}&= \frac{1}{2} \times {\rm{3}} \times {\rm{4}}\\& = {\rm{6}}\;{\rm{c}}{{\rm{m}}^2}\end{align}\)

(d) Given

Base \(= 3 \,\rm cm\)

Height \(= 2 \,\rm cm\)

\(\begin{align}&\text{Area of triangle} \\ &= \frac{1}{2} \times {\rm{Base}} \times {\rm{Height}} \end{align}\)

\(\begin{align}& = \frac{1}{2} \times {\rm{3}} \times {\rm{2}}\\&= {\rm{3}}\;{\rm{c}}{{\rm{m}}^2}\end{align}\)

  
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