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Mathematics

Assertion (A): In the figure, if AD = DC = 4 cm, EC = 10 cm and DE || AB, then CE = 5 cm.

Reason (R): The straight line drawn through the mid-point of one side of a triangle parallel to other, bisects the third side.

In the given figure, P is a point in the interior of ∠ABC. If PL ⊥ BA and PM ⊥ BC such that PL = PM, prove that BP is the bisector of ∠ABC.R.S. Aggarwal Mathematics Solutions ICSE Class 9.
  1. A is true, R is false

  2. A is false, R is true

  3. Both A and R are true

  4. Both A and R are false

Mid-point Theorem

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Answer

By converse of mid-point theorem,

A line drawn through the midpoint of one side of a triangle, and parallel to another side, will bisect the third side.

∴ Reason (R) is true.

In △ABC,

Since, D is the mid-point of AC and DE // AB, thus C is mid-point of BC.

CE = BE

From figure,

BC = CE + BE = CE + CE = 2 CE

⇒ CE = 12BC=12\dfrac{1}{2}BC = \dfrac{1}{2} × 10 = 5 cm.

∴ Assertion (A) is true.

Hence, option 3 is the correct option.

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