Math Problem Statement

D, E, F are midpoints of sides AB, BC and CA of ΔABC, if ar(ΔABC) = 64 cm² then, area of ΔBDE is

Solution

Let's analyze and solve this problem step by step.

Given:

  • DD, EE, and FF are midpoints of sides ABAB, BCBC, and CACA of ABC\triangle ABC.
  • Area of ABC=64cm2\text{Area of } \triangle ABC = 64 \, \text{cm}^2.
  • We need to find the area of BDE\triangle BDE.

Concept:

Since DD, EE, and FF are the midpoints of ABAB, BCBC, and CACA, the line segments DEDE, EFEF, and FDFD form a smaller triangle inside the original triangle ABC\triangle ABC.

Median Triangle Theorem:

When we connect the midpoints of a triangle, the triangle formed (here DEF\triangle DEF) will have an area that is exactly one-fourth of the area of the larger triangle ABC\triangle ABC. Therefore, the area of DEF\triangle DEF will be: Area of DEF=14×64cm2=16cm2.\text{Area of } \triangle DEF = \frac{1}{4} \times 64 \, \text{cm}^2 = 16 \, \text{cm}^2.

However, we are asked to find the area of BDE\triangle BDE, which is half of ABC\triangle ABC due to the fact that we are only considering part of the triangle formed by two medians and the side BDBD.

Solution:

The triangle BDE\triangle BDE is one-fourth the area of the whole triangle ABC\triangle ABC, because we are dividing it by the medians, and thus it will also have an area of 16cm216 \, \text{cm}^2.

Answer:

The area of BDE\triangle BDE is 16 cm² (Option C).

Would you like further details on this or have any other questions?

Here are 5 related questions to expand your understanding:

  1. How does the area of a median triangle compare to the area of the original triangle?
  2. What is the centroid theorem, and how does it relate to midpoints in a triangle?
  3. How do you find the area of a triangle given its vertices using coordinates?
  4. How would the area change if DD, EE, and FF were not midpoints?
  5. What is the significance of medians in dividing a triangle into equal-area sections?

Tip: When solving geometry problems, always remember that median lines and midpoint connections divide a triangle into proportional areas!

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Math Problem Analysis

Mathematical Concepts

Geometry
Triangles
Midpoint Theorem
Area Calculation

Formulas

Area of ΔDEF = (1/4) × Area of ΔABC
Area of ΔBDE = Area of ΔABC ÷ 4

Theorems

Midpoint Theorem
Median Triangle Theorem

Suitable Grade Level

Grades 9-10