Q&A for How to Calculate the Area of a Trapezoid

You have to know the lengths of both bases (as well as the height) in order to find the area.

You're actually finding the average of the two bases first (by adding their lengths and dividing by two) and then multiplying by the height.

Yes. Even though not all trapezoids are the same size, it will still work if you plug the numbers in correctly.

Use the reverse formula: If the Area of a trapezoid is (B1+B2)*h/2, then to check your answer attempt to find one of the other values. For example, attempt to find h (height); h = A*2/(B1+B2). If the answer you've just calculated is the same as the value that the problem gives you for h (and assuming your calculations are exact), then the Area is correct. This procedure also works for B1 and B2, B1 = [(A*2)-B2]/h, B2 = [(A*2)-B1]/h.

Divide the area by the height.

The ratio between the circumference of a circle and its diameter is always the same for any circle, no matter how large or small the circle is, and it is equal to approximately 3.1415. So, to calculate the circumference of the circle, simply multiply its diameter with 3.1415.

You would also have to know the area. Divide the area by half the sum of the bases.

A figure is a trapezoid if it has four sides, two -- and only two -- of which are parallel to each other. The parallel sides must be of unequal length.

Yes, that works.

Add the two bases together and divide by two. Then take that number and divide it into the area. That will give you the height.

Reworking the formula, h=(2A) ÷ (b+B).

That's called a right trapezoid.

To make sense of this, you should draw the trapezoid, letting the upper base be 5 and the lower base be 17. Then drop two heights (h) from the upper-left and upper-right corners to the lower base. Then do the following: Subtract the shorter base from the longer base, and divide by 2. (This works only with an isosceles trapezoid.) That gives you 6, which is the distance from either lower corner to the point where the height lines meet the lower base. Using the Pythagorean Theorem, 6² + h² = 10². Therefore, h² = 10² - 6² = 64. So h = 8. Use the formula above to find the area.

A trapezoid is defined as having two parallel bases, so there would be only one height.

Other than the fact that they are parallel, there is no specific relationship.

You can solve the problem multiple times and if you continue to get the same answer, chances are that you got it correct.

Measure the width at the bottom and top of the trapezoid.

You round the bases and height to the nearest whole number and then you do the same process.

A stands for area, which is what you are trying to find.

Because the "bases" of a trapezoid are parallel to each other, a trapezoid can have only one "height," which is the distance between the bases.

That is often the case with trapezoids. As long as the two "bases" are parallel to each other, you can use the area formula given in the above article.

You have to know both bases. You can't do it otherwise.

Use the regular formula. The two non-parallel sides do not have to be equal in length.

The length of the median of a trapezoid is the average of the lengths of the two bases. In other words, it's half their sum. So [(x - 14) + (x + 2)] / 2 = 30. Then (x - 14) + (x + 2) = 60. So 2x -12 = 60, 2x = 72, and x = 36. Thus, the shorter base is 36 - 14 = 22 cm.

See Find the Perimeter of a Trapezoid.

No. The text above is correct. The formula for a trapezoid's area is "height multiplied by half the sum of the bases" (in other words, "height times median.")

Let "x" be the major base. Then 4x/5 is the minor base. So x - (4x/5) = (5x/5) - (4x/5) = x/5 = 12, and x = 60. Then the minor base is 60 - 12 = 48. Half the sum of the bases is (60 + 48) / 2 = 54. The area is (54)(36) = 1944 sq cm.

Yes. The "bottom" of a trapezoid is usually called "the base," but actually each of a trapezoid's parallel sides is considered a base (b1 and b2 in the area formula).

What you're describing sounds like a rectangle. It's unclear what you mean by "4 values." The formula for the area of a trapezoid does work for a rectangle.

Use the area formula given in the article above. The trapezoid does not have to be isosceles for the formula to work.