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Lesson 2: Area of parallelograms and triangles

# Finding area of triangles

The area of a triangle is found by multiplying one half of the base by the height. In our example, the base is 18 and the height is 6. So, half of 18 is 9, and 9 times 6 equals 54 square units.

## Want to join the conversation?

• In a case when the height isn't given, how do you find out the height?
• 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
• Can I also write the solution like this:b*h/2?
• Yes you can because it is the same thing as 1/2*b*h because of the communative property
• 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?
• what if your base or height is a fraction? PLS HELP ME!
• If the base or height is a fraction, then do the formula as normal. If one is a fraction, and the other isn't, make the whole number a fraction, for example, 3= 3/1. Hope this helps!
• I don't understand this, because my teacher told me to do base times height or length times width and then divided by 2 but, he/she said 1/2 x base/width x height/length. Are they both same
• you only divided 2 when you are doing 1/2 b x h
• The reason why is because then you will get a different product, which will result in a different area.
• How do I find the perimeter of a triangle?
• OK, is it just base times height and then divide by two? i am kinda confused. can some one plz help me?