I need perimeter and area help. (triangle, pentagon)?

Question

I am helping my sister study and I just need some tips, I can't explain it in a way she understands. Please help.

Oh yes and in case you haven't noticed I only need triangle and pentagon help, she gets square anb rectangle, pleses note she is only in 6th grade.

Answer 1

If she understands how the area of a rectangle works, you can show her how a rectangle is always made of two triangles. Any triangle can be 'doubled' to form another parallelogram. A corner of a parallelogram can be 'chopped off' and moved to the other side to create a true rectangle.

Once she understands this thouroghly, you can proceed to demonstrate how a pentagon can be broken into triangles.

Answer 2

The perimeter of both the triangle and the pentagon are just the sum of all the sides. If you have a triangle measuring 2" on one side, 3" on another, and 4" on the last, then the perimeter is 9" , use this same method for the five sides of a pentagon.

The area is measured in units squared as you know from the rectangle. For a triangle, this is found using the formula

1/2 Base X Height

If you imagine an equilateral triangle, you and cut it in half, and flip it over on top of the other half to make a rectangle, thus proving your equation.

For the pentagon, I'm assuming it is an equilateral pentagon, meaning all sides are the same. If you draw lines from the points into the center, you'll notice you have 5 equal triangles. Using the Pythagorean theorem,

a^2 + b^2 = c^2

you can find the height of one triangle, then using the triangle area problem

1/2Base X Height

Multiplying the one triangle of the pentagon by 5 will give you the total area of the pentagon.

Answer 3

Since she is only in the 6th grade, I guess what you need is the area of a regular pentagon (a pentagon with all the sides equal). This kind of pentagon can be inscribed in a circle. Now you take the center of the circle and you connect it with the vertices of the pentagon. You will obtain five triangles. Since you can easily find the area of a triangle (base * height corresponding to that base / 2) you just sum up all these five areas and what you get is the area of the pentagon.

In case of an irregular pentagon, the method is the same, just that in this case you don't consider the center of any circle, but just an arbitrary point INSIDE (!) the pentagon.

Another method for finding the area of a triangle without computing the height is by using Heron's formula. I'm too lazy to write it here since I cannot format the text, so visit this page on wikipedia: http://en.wikipedia.org/wiki/Heron's_formula

Answer 4

perimeter you just need to add up all the sides and the triangle and pentagon need a formula to find area. Triangle is base times height divided by two. And i have no idea on the pentagon SORRY:(

Answer 5

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RE:
I need perimeter and area help. (triangle, pentagon)?
I am helping my sister study and I just need some tips, I can't explain it in a way she understands. Please help.