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It is given that ∆ABC ≅ ∆FDE and AB = 5 cm, ∠B = 40° and ∠A = 80°. Then which of the following is true?

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Question

It is given that ∆ABC ≅ ∆FDE and AB = 5 cm, ∠B = 40° and ∠A = 80°. Then which of the following is true?

Options

  • DF = 5 cm, ∠F = 60°

  • DF = 5 cm, ∠E = 60°

  • DE = 5 cm, ∠E = 60°

  • DE = 5 cm, ∠D = 40°

MCQ
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Solution

DF = 5 cm, ∠E = 60°

Explanation:

Given, ∆ABC ≅ ∆FDE and AB = 5 cm, ∠B = 40°, ∠A = 80°

Since, ∆FDE ≅ ∆ABC


∴ DF = AB   ...[By CPCT]

DF = 5 cm  

And ∠E = ∠C   ...[By CPCT]

⇒ ∠E = ∠C = 180° – (∠A + ∠B)  ...[By angle sum property of a ∆ABC]

⇒ ∠E = 180° – (80° + 40°)

⇒ ∠E = 60°

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Chapter 7: Triangles - Exercise 7.1 [Page 64]

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NCERT Exemplar Mathematics Exemplar [English] Class 9
Chapter 7 Triangles
Exercise 7.1 | Q 7. | Page 64

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