CBSE Class 10 Mathematics Standard sample paper 2023-24: question 8
From the official CBSE sample question paper for 2023-24, section A, question 8, for 1 mark. Try it first; the hints and our step-by-step solution are below.
Q8 · 1 mark · MCQTriangles
In ABC, DE AB. If AB = a, DE = x, BE = b and EC = c. Then x expressed in terms of a, b and c is:
- (A)
- (B)
- (C)
- (D)
Figure in the paper: Triangle ABC with A at top left, B at bottom left, C at bottom right. D lies on side AC and E lies on side BC, with DE parallel to AB. Labels: AB = a, DE = x, BE = b, EC = c. See it in the official paper.
Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.
Hints
Open one hint at a time and try again before the next.
Hint 1
A line parallel to one side gives a smaller similar triangle.
Hint 2
. Compare DE with AB.
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.
Since , (AA similarity: is common and corresponding angles are equal).
So , which gives .
- 1 mark
Therefore . Option (B).
Answer: , option (B)
Where the marks are
- Uses to get , option (B) (1 mark)
Revise the chapter
- Chapter: Triangles (notes, formulas, where marks are lost and every past question)
- Topic: Basic Proportionality Theorem (Thales Theorem)
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