Trapezoid Area Calculation: Verifying and Applying the Formula with 4cm and 7cm Parallel Sides

Trapezoid Area Formula with Missing Height

ABCD is a trapezoid.

AB = 4 cm

DC = 7 cm

BK = 6 cm

Can the trapezoidal area formula be applied? If so, apply it and calculate.

444777666AAABBBCCCDDDKKK

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Can we calculate the area of the trapezoid? If yes, calculate it
00:03 We'll use the formula for calculating trapezoid area
00:08 (Sum of bases(AB+DC) multiplied by height(H)) divided by 2
00:20 We know the side lengths but not the height
00:24 Therefore, we cannot calculate the trapezoid's area
00:29 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

ABCD is a trapezoid.

AB = 4 cm

DC = 7 cm

BK = 6 cm

Can the trapezoidal area formula be applied? If so, apply it and calculate.

444777666AAABBBCCCDDDKKK

2

Step-by-step solution

The formula for the area of a trapezoid is:

S=(AB+DC)×h2 S=\frac{(AB+DC)\times h}{2}

Since we are given AB and DC but not the height, we cannot calculate the area of the trapezoid.

3

Final Answer

It cannot be applied.

Key Points to Remember

Essential concepts to master this topic
  • Formula Requirements: Trapezoid area needs both parallel sides and height
  • Height vs Side: BK = 6 cm is a slanted side, not perpendicular height
  • Check Complete Info: Verify all required measurements before applying formula ✓

Common Mistakes

Avoid these frequent errors
  • Using any given measurement as height
    Don't use BK = 6 cm as the height in S=(AB+DC)×h2 S=\frac{(AB+DC)\times h}{2} = wrong area! BK is a slanted side length, not the perpendicular distance between parallel sides. Always identify the true height (perpendicular distance) before applying the trapezoid area formula.

Practice Quiz

Test your knowledge with interactive questions

Given the following trapezoid:

AAABBBCCCDDD584

Calculate the area of the trapezoid ABCD.

FAQ

Everything you need to know about this question

Why can't I use BK = 6 cm as the height?

+

BK is a slanted side of the trapezoid, not the height! The height must be the perpendicular distance between the two parallel sides AB and DC.

What measurements do I need for trapezoid area?

+

You need three things: the lengths of both parallel sides (we have AB = 4 cm and DC = 7 cm) plus the perpendicular height between them (which we don't have).

How is trapezoid height different from triangle height?

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In a trapezoid, height is always the perpendicular distance between the parallel sides. It's never measured along a slanted side like BK.

Can I find the height using the given information?

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Not with just these measurements! You'd need additional information like angles or coordinates to calculate the perpendicular height from the slanted side BK = 6 cm.

What should I do when the formula can't be applied?

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Always check if you have all required measurements first. If something is missing (like height here), state clearly that the formula cannot be applied rather than guessing.

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