CBSE Class 10 Mathematics Basic 2025: question 8
Set in the CBSE Class 10 board exam of 2025, paper 430/2/1, 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 the given figure, if DE BC, AD = 1.5 cm, DB = 3 cm and EC = 2 cm, the length of AC is :
- (A)1.5 cm
- (B)3 cm
- (C)3.5 cm
- (D)4.5 cm
Figure in the paper: Triangle ABC with A at the top. D lies on side AB and E lies on side AC, with DE parallel to BC. AD = 1.5 cm and DB = 3 cm are marked on AB; EC = 2 cm is marked on AC. Arrows show DE parallel to BC. See it in the official paper.
Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 430/2/1.
Hints
Open one hint at a time and try again before the next.
Hint 1
DE ∥ BC — which theorem applies?
Hint 2
Find AE first, then add EC.
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.
By the Basic Proportionality Theorem, , so , giving AE = 1 cm.
- 1 mark
AC = AE + EC = 1 + 2 = 3 cm, which is option (B).
Answer: 3 cm, option (B)
Where the marks are
- Uses BPT to get AE = 1 cm and AC = 3 cm (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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