Ex.10.4 Q3 Practical Geometry Solution- NCERT Maths Class 7

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Examine whether you can construct \(ΔDEF\) such that \(EF = 7.2\,\rm{ cm},\) \(m∠E = 110^\circ\) and \(m∠F = 80^\circ. \)Justify your answer.

 Video Solution
Practical Geometry
Ex 10.4 | Question 3

Text Solution

What is known?

Length of one side of a triangle and measure of two angles.

What is unknown?

Whether a triangle be constructed with the given values of length and angles.


By using the angle sum property, we can find out the third angle. If the angle sum property is followed, then it is possible to construct a triangle and if not then we cannot construct a triangle.


We will use angle-sum property of a triangle to find the measure of \(∠D\)

By angle sum property,

\(∠E +∠F + ∠D =\) \(180^\circ .\)

\(110^\circ + 80^\circ + ∠D =\) \(180^\circ. \)

\(190^\circ + ∠D\) \(=\) \(180^\circ .\)

So, \(∠D = -10^\circ\)

Angle of \(-10^\circ\) is not possible, thus we cannot construct triangle \(ΔDEF.\)

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