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Question

In triangle ABC, DE is drawn parallel to BC, intersecting AB and AC at D and E respectively. If AD=3, DB=6, and AE=4, find EC.

This question was previously asked in
SSC CGL 2025 Tier 2 Paper 1 Question Paper (19-Jan-2026)
The correct answer is

8

Geometry Problem: Finding EC in Triangle ABC

The problem involves a triangle ABC where a line segment DE is drawn parallel to BC, intersecting sides AB and AC at points D and E, respectively. We are given the lengths AD = 3, DB = 6, and AE = 4, and we need to find the length of EC.

Applying the Basic Proportionality Theorem

When a line is drawn parallel to one side of a triangle intersecting the other two sides, it divides the two sides proportionally. This is known as the Basic Proportionality Theorem (BPT) or Thales's Theorem.

According to the BPT, for triangle ABC with DE || BC:

$ \frac{AD}{DB} = \frac{AE}{EC} $

Calculation Step-by-Step

  1. Substitute Given Values: Plug the known lengths into the BPT formula:

    $ \frac{3}{6} = \frac{4}{EC} $

  2. Simplify the Ratio: Simplify the fraction on the left side:

    $ \frac{1}{2} = \frac{4}{EC} $

  3. Solve for EC: Cross-multiply to find the value of EC:

    $ 1 \times EC = 2 \times 4 $

    $ EC = 8 $

Therefore, the length of EC is 8.

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Important Questions from Triangles, Congruence and Similarity

  1. The radius of the circumcircle of an equilateral triangle of √3 unit side, is:

  2. If the ratio of the angles of a triangle is 3 : 5 : 7, find the value of the largest angle.

    A. 36°

    B. 60°

    C. 84°

    D. 15°

  3. If ΔABC and Δ PQR are similar and \(\rm\frac{BC}{QR} = \frac{1}{3}\) , find  \(\rm\frac{ar(\Delta PQR)} {ar(\Delta BCA)}\)

  4. If the angles of a triangle are in the ratio of 2 : 5 : 8, then find the value of the smallest angle.

  5. ABCD is a parallelogram. Side BC is produced to E such that BC = CE. Join AE which intersects side CD at P. The area of triangle ABE is:

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