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Quantitative Aptitude

TRIANGLES MCQs

Total Questions : 83 | Page 9 of 9 pages
Question 81. ∠A of ΔABC is a right angle. AD is perpendicular on BC. If BC = 14 and BD = 5 cm, then measure of AD is:
  1.    $$\sqrt 5 $$ cm
  2.    $$3\sqrt 5 $$ cm
  3.    $$3.5\sqrt 5 $$  cm
  4.    $$2\sqrt 5 $$ cm
 Discuss Question
Answer: Option B. -> $$3\sqrt 5 $$ cm
AD2 = BD × DC
AD2 = 5 × 9
AD = $$\sqrt {45} $$
AD = $$3\sqrt 5 $$  cm
Question 82. If two medians BE and CF of a triangle ABC, intersect each other at G and if BG = CG, ∠BGC = 60°, BC = 8 cm, then area of the triangle ABC is:
  1.    $$96\sqrt 3 $$  cm2
  2.    $$48\sqrt 3 $$  cm2
  3.    48 cm2
  4.    $$54\sqrt 3 $$  cm2
 Discuss Question
Answer: Option B. -> $$48\sqrt 3 $$  cm2
According to question,
⇒ ∵ ∠BGC = 60° (given)
⇒ ∠GBC = ∠GCB = x°
⇒ x° + x° + 60° = 180°
⇒ x = 60°
⇒ So ΔBGC is an equilateral triangle with side 8 cm each
Then,
Area pf triangle ΔBGC
= $$\frac{{\sqrt 3 }}{4}$$ a2
= $$\frac{{\sqrt 3 }}{4}$$ 82
= 16$${\sqrt 3 }$$ cm2
⇒ Area of ΔABC
= Area (ΔBGC + ΔAGC + ΔAGB)
⇒ Area of ΔABC = 3 × 16$${\sqrt 3 }$$
⇒ Area of ΔABC = 48$${\sqrt 3 }$$ cm2 {∵ ΔBGC = ΔAGC = ΔAGB}
Question 83. For a triangle ABC, D, E, F are the mid - point of its sides. If ΔABC = 24 sq. units then ΔDEF is :
  1.    4 sq. units
  2.    6 sq. units
  3.    8 sq. units
  4.    12 sq. units
 Discuss Question
Answer: Option B. -> 6 sq. units
According to question,
As we know that
Given: area of ΔABC = 24 square units
As we know that
D, E and F are the midpoint of AB, AC and BC
∴ Area of ΔADE = area of ΔDBF
= area of ΔDEF = area of ΔEFC
∴ Area of ΔDEF = $$\frac{1}{4}$$ area of ΔABC
Area of ΔDEF = $$\frac{1}{4}$$ × 24
Area of ΔDEF = 6 sq. units

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