Calculate Triangle Area with 1/5 Ratio: Height-Base Geometry Problem

Triangle Area with Ratio-Based Dimensions

Since the side BC is 15 \frac{1}{5} side AE.

Calculate the area of the triangle:

101010AAABBBCCCEEE

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Calculate the triangle's area
00:06 BC equals one-fifth of AE according to the given data
00:12 Substitute in the value of AE in order to determine BC
00:18 Apply the formula for calculating the area of a triangle
00:21 (base(BC) x height(AE)) divided by 2
00:26 Substitute in the relevant values and calculate to determine the area
00:32 Reduce the 2
00:36 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Since the side BC is 15 \frac{1}{5} side AE.

Calculate the area of the triangle:

101010AAABBBCCCEEE

2

Step-by-step solution

To solve the problem, we will follow these steps:

  • Step 1: Using AE=10 AE = 10 , calculate BC BC using the information that BC=15×AE BC = \frac{1}{5} \times AE .
  • Step 2: Apply the formula for the area of a triangle.

We proceed with the calculations:
Step 1: Since BC=15×10=2 BC = \frac{1}{5} \times 10 = 2 .
Step 2: Assume AB AB is perpendicular to BC BC to apply the formula Area=12×base×height \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} .

The triangle ABC\triangle ABC is vertical, implying that base BC BC and height AE AE can be used because it suggests AE AE is perpendicular to BC BC. Thus,
Area=12×AE×BC=12×10×2=10\text{Area} = \frac{1}{2} \times AE \times BC = \frac{1}{2} \times 10 \times 2 = 10.

Therefore, the area of the triangle is 1010.

3

Final Answer

10

Key Points to Remember

Essential concepts to master this topic
  • Given Ratio: Use BC = 1/5 × AE to find base length
  • Height Identification: AE = 10 serves as perpendicular height to base BC
  • Area Verification: Check that 1/2 × 10 × 2 = 10 square units ✓

Common Mistakes

Avoid these frequent errors
  • Using AE as the base instead of BC
    Don't use AE = 10 as the base with BC = 2 as height = Area of 1/2 × 10 × 2 calculated wrong! The perpendicular height AE should multiply with the actual base BC. Always identify which measurement is the base and which is the perpendicular height from the diagram.

Practice Quiz

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What is the ratio between the orange and gray parts in the drawing?

FAQ

Everything you need to know about this question

How do I know which side is the base and which is the height?

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Look at the diagram carefully! The height is always perpendicular (forms a 90° angle) to the base. Here, AE is drawn vertically and perpendicular to the horizontal base BC.

Why do we use the ratio 1/5 to find BC?

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The problem states that BC is 15 \frac{1}{5} of side AE. Since AE = 10, we calculate: BC = 1/5 × 10 = 2. This gives us the actual length of the base.

What if I calculated BC = 1/5 × 10 = 0.2 instead of 2?

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Be careful with your arithmetic! 15×10=105=2 \frac{1}{5} \times 10 = \frac{10}{5} = 2 , not 0.2. Remember that dividing by 5 is the same as multiplying by 1/5.

Can I use a different formula for triangle area?

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The standard formula Area=12×base×height \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} works best here because we have a clear perpendicular height. Other formulas like Heron's formula would be unnecessarily complicated.

How do I check if my answer of 10 is correct?

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Verify by checking the calculation: Area=12×2×10=202=10 \text{Area} = \frac{1}{2} \times 2 \times 10 = \frac{20}{2} = 10 . The numbers should make sense with the given ratio and measurements! ✓

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