The base BC of a triangle ABC is divided at D such that BD = half of DC. The area of triangle ABC is _________ times the area of triangle ADC.
- AOption (a)
three
- BOption (b)
four
- COption (c)
two
- DOption (d)
View answer & explanationHide answer & explanation
Correct answer
Why this answer is correct
Shortcut Trick
Triangles sharing a common vertex have their areas in the direct ratio of their bases.
Given, BD = (1/2) × DC ⇒ DC = 2 × BD
Total base BC = BD + DC = BD + 2 × BD = 3 × BD
Therefore, the ratio of the area of triangle ABC to triangle ADC is:
Area(ABC) ÷ Area(ADC) = BC ÷ DC = (3 × BD) ÷ (2 × BD) = 3/2
∴ The correct answer is (3)/(2) times.
Alternate Method
Given:
In triangle ABC, the base BC is divided at D such that BD = (1/2) × DC.
Formula Used:
Area of a triangle = (1/2) × Base × Height
Calculations:
Let the length of BD be x.
⇒ DC = 2x
⇒ BC = BD + DC = x + 2x = 3x
Let h be the perpendicular height from vertex A to the base BC.
⇒ Area of triangle ABC = (1/2) × BC × h = (1/2) × 3x × h
⇒ Area of triangle ADC = (1/2) × DC × h = (1/2) × 2x × h
Now, let us find the ratio of the area of triangle ABC to the area of triangle ADC:
⇒ Area(ABC) ÷ Area(ADC) = ((1/2) × 3x × h) ÷ ((1/2) × 2x × h)
⇒ Area(ABC) ÷ Area(ADC) = 3x ÷ 2x = 3/2
⇒ Area(ABC) = (3/2) × Area(ADC)
Thus, the area of triangle ABC is (3/2) times the area of triangle ADC.
Let us analyze why the other options are incorrect:
Option (1) is incorrect because a ratio of 3 would require the base BC to be 3 times DC, which is false since BC is 1.5 times DC.
Option (2) is incorrect because a ratio of 4 would require the base BC to be 4 times DC.
Option (3) is incorrect because a ratio of 2 would require the base BC to be 2 times DC.
∴ The correct answer is (3)/(2) times.
Additional Information
Triangles with a Common Vertex
When two or more triangles share a common vertex and have their bases on the same straight line, their perpendicular heights are equal. Consequently, the ratio of their areas is equal to the ratio of their bases.
Median of a Triangle
A median divides a triangle into two triangles of equal area because it bisects the base, making the ratio of the bases 1:1.
Area Ratio Theorem
For any triangle ABC with a point D on BC, the ratio of the areas of the two sub-triangles is given by Area(ABD) ÷ Area(ADC) = BD ÷ DC.









