CBSE Class 10 Mathematics Basic 2025: question 31
Set in the CBSE Class 10 board exam of 2025, paper 430/5/1, section C, question 31, for 3 marks. Try it first; the hints and our step-by-step solution are below.
Q31 · 3 marks · Short answerTriangles
Point E lies on the extended side AD of parallelogram ABCD. BE intersects CD at F. Show that (i) (ii) .
Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 430/5/1.
Hints
Open one hint at a time and try again before the next.
Hint 1
In a parallelogram opposite sides are parallel, so AE ∥ BC. Which alternate angles does transversal EB create?
Hint 2
For (ii), use that opposite angles of a parallelogram are equal, together with one pair of alternate angles.
Step-by-step solution
Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.
- ½ mark
Figure: parallelogram ABCD with side AD produced beyond D to a point E; segment BE cuts side CD at F. Since ABCD is a parallelogram, AE ∥ BC and AB ∥ DC.
- 1 mark
(i) In △DFE and △CFB:
[alternate interior angles, DE ∥ BC, transversal EB]
[alternate interior angles, DE ∥ BC, transversal DC] - ½ mark
∴ [AA similarity criterion]
- ½ mark
(ii) In △AEB and △CBF:
[alternate interior angles, AE ∥ BC]
[opposite angles of a parallelogram are equal, ] - ½ mark
∴ [AA similarity criterion]
Answer: (i) △DFE ~ △CFB by AA; (ii) △AEB ~ △CBF by AA.
Where the marks are
- Correct figure (½ mark)
- Two pairs of equal angles in △DFE and △CFB with reasons (1 mark)
- Concludes △DFE ~ △CFB by AA (½ mark)
- Two pairs of equal angles in △AEB and △CBF with reasons (½ mark)
- Concludes △AEB ~ △CBF by AA (½ mark)
Revise the chapter
- Chapter: Triangles (notes, formulas, where marks are lost and every past question)
- Topic: Problems on Similar Triangles
More questions from Triangles
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The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.