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## Get ready for 7th grade

### Unit 5: Lesson 2

Area of parallelograms and triangles# Finding area of triangles

To find a triangle's area, use the formula area = 1/2 * base * height. Choose a side to use for the base, and find the height of the triangle from that base. Then, plug in the measurements you have for the base and height into the formula.

## Want to join the conversation?

- In a case when the height isn't given, how do you find out the height?(30 votes)
- In that case, you would use the Pythagorean theorem. That's a squared plus b squared equals c squared. In this specific scenario, the hypotenuse is already given and you would need to know one of the sides or legs in the equation. That means you would square the hypotenuse (the side not connected to a right angle), subtract the square of the side/leg you already know, then take the square root of that final number. That would be the height of the triangle(32 votes)

- Can I also write the solution like this:b*h/2?(14 votes)
- Yes you can because it is the same thing as 1/2*b*h because of the communative property(1 vote)

- How do I find the perimeter of a triangle?(5 votes)
- What if instead you need to find the height and not area?(5 votes)
- If you need the height and have the area and width, you can simply just take the area and divide it by the width, then you will get the height. If you want to double-check my theory you can multiply the width by the number you got and if it equals the area then yes, that is the length.(1 vote)

- So what I understand is base times height divided by one half is the area? What about a triangle flipped over or to the side. I would like a simplyfied version(4 votes)
- I'm not sure what you mean... I assume you are talking about right triangles, in that case, the position or form of the triangle is irrelevant to the equation. No matter what type of triangle it is, whether it be a right triangle, isosceles triangle, or equilateral triangle, this method and equation works for all 3 sided shapes. Hope this helps.(2 votes)

- is it possible to find the area of a human

A= .5 B*H(3 votes)- In fact, it is! Although it is super complicated. A man once tried to find the area of his leg! Although, your equation doesn't match up because this is focused on triangles, not bodies.

The real equation would be:

"Calculate weight in kilograms: 210 pounds ÷ 2.2 = 95.45 kg.

Calculate height in centimeters: 6 feet, 3 inches = 75 inches x 2.54 cm/inch = 190.5 cm.

Multiply height by weight and divide by 3600. (190.5 cm x 95.45 kg) ÷ 3600 = 5.

Take the square root of 5 = 2.24 m2"

Note: I give credit to the person who did the calculations.(3 votes)

- This is perhaps a silly question, if so sorry. (Or perhaps covered later?)

Since the length of a triangle’s sides is correlated to the triangle’s angles, shouldn’t it follow that you could calculate the area of a triangle with only the measure of it’s angles?(3 votes) - how do you find the height without it giving it(3 votes)
- how do you Never gonna give you up, Never gonna let you down, Never gonna run around and desert you(3 votes)
- OK, is it just base times height and then divide by two? i am kinda confused. can some one plz help me?(2 votes)
- Yes, it is! Whenever finding the area of a triangle, you always want to multiply the base by the height then divide that all by 2. (bh)/2(3 votes)

## Video transcript

- [Instructor] What is
the area of the triangle? And they're talking
about this triangle here. And like always, pause this video and see if you can figure
it out on your own. Alright, now let's work
through it together. So we know that the area of a triangle is going to be equal to one half times our base, times our height. Let me do the height in a different color. Times our height. So what is the length of
our base in this scenario? Well the base is this 18 right over here. Let me highlight it. This length right over here is our base. So the base is 18, and what is the height? Well the height we see is six. They give it to us. They don't always give it to you, but in this example they do. So the height is, the height, the height is, I'm having
trouble with my pen, is six, so now we just have to compute what one half times 18 times six is. Well let's think about this a little bit. One half times 18 is nine. Nine times six is equal to what? Nine times six is equal to 54. And we're done. This is 54 square units.