Finding Area of triangle and trapezoid

[Cindy Burgess]

I am trying to finish a homework assignment and I'm not sure what Area=47.8cm^2 means (Why the square of the centimeter?) Does that mean I have to do something different when finding the missing measurement? Round your answer to the nearest tenth.

1. The base of a triangle = x (unknown). The height = 8.1 cm and the Area =47.8 cm^2. Here is how I tried to work it: (8.1x)/2 = 45.8. Next, multiply both sides by 2, leaving 8.1x = 91.6. Divide 91.6/8.1 x=11.3 cm

2. The height of a trapezoid's right angle side is 5 in. The base is x and the area is 60 in^2. Here is how I tried to work it: 60 in^2= 5(b1 + b2).
60in^2=5(6+6) The unknown is 6 in.

3. The height of a trapezoid is x mi. B1 = 3.3 mi and B2 = 7.3 mi The area = 29.2 mi^2. Here is how I tried to work it: 29.2 mi^2=x(3.3+7.3)
29.2mi^2=10.6x. Divide each side by 10.6. 2.1 mi = x.

4. A=38.9 km^2 38.9km^2= The height 6.7 (3.6 km + x km). I divided 6.7 into 38.9 and got 5.8. Then I took 3.6 away from 5.8 and got x=2.2 km.

Did I do these right? Again why is the area written with a square of 2?

Thanks,
Cindy

 

[JeffM]

Again why is the area written with a square of 2?

Thanks,
Cindy

A centimeter is a measure of the length of the line. We measure areas in terms of little squares. So when we say that a triangle has a certain area we mean that it has the same area as a certain number of squares. So if we are using squares with a length of each side = 1 centimeter the area of one square is one centimeter squared. We do the same thing with feet. Areas are measured in square feet. It goes on to volumes where we measure with little cubes. So we talk about cubic centimeters or cubic feet. Make sense now?

 

[Deleted member 4993]

I am trying to finish a homework assignment and I'm not sure what Area=47.8cm^2 means (Why the square of the centimeter?) Does that mean I have to do something different when finding the missing measurement? Round your answer to the nearest tenth.

1. The base of a triangle = x (unknown). The height = 8.1 cm and the Area =47.8 cm^2. Here is how I tried to work it: (8.1x)/2 = 45.8. Next, multiply both sides by 2, leaving 8.1x = 91.6. Divide 91.6/8.1 x=11.3 cm ..... Correct ... You check your answer by calculating the area with b = 11.3 an h = 8.1

2. The height of a trapezoid's right angle side is 5 in. The base is x and the area is 60 in^2. Here is how I tried to work it: 60 in^2= 5(b1 + b2).
60in^2=5(6+6) The unknown is 6 in..... This problem seems to be missing data. Please review and correct.

3. The height of a trapezoid is x mi. B1 = 3.3 mi and B2 = 7.3 mi The area = 29.2 mi^2. Here is how I tried to work it: 29.2 mi^2=x(3.3+7.3)/2
29.2mi^2=10.6x. Divide each side by 10.6. 2.1 mi = x. Incorrect - fix it by fixing the area equation and associated arithmetic. Check your answer by recalculating the area.

4. A=38.9 km^2 38.9km^2= The height 6.7 (3.6 km + x km). I divided 6.7 into 38.9 and got 5.8. Then I took 3.6 away from 5.8 and got x=2.2 km. ... Please review your post and correct it.

Did I do these right? Again why is the area written with a square of 2?

Thanks,
Cindy

.

 

[Cindy Burgess]

Yes, that does make sense. I just didn't know if somehow I had to square something myself or find the square root, but now I know that I don't have too. Will you please check my answers. It's the first time that I've done my work this way where I am looking for a number.

 

[Cindy Burgess]

2. The height of a trapezoid's right angle side is 5 in. Neither base is listed. Therefore, I assigned one base to be x. I assume the other base will be the same number as x in that one of the examples the teacher gave us was like that. The area is 60 in^2. I used A= h(b1 + b2). Therefore: 60 in^2= 5(x + x). Knowing that 12 x 5 = 60. I determined that x had to be 6?

**This problem seems to be missing data. Please review and correct. I have listed more information and corrected this problem.

3. The height of a trapezoid is x mi. B1 = 3.3 mi and B2 = 7.3 mi The area = 29.2 mi^2. Here is how I tried to work it: 29.2 mi=x(3.3+7.3)/2 Why did you divide by 2? Wouldn't it be A=H(b1+b2). Wouldn't that be 29.2 = x (3.3+7.3=10.6) or 10.6x 29.2=10.6x Divided each side by 10.6--
x=2.8 mi
** I've corrected my problem. Now is it correct? Incorrect - fix it by fixing the area equation and associated arithmetic. Check your answer by recalculating the area.

4. A=38.9 km^2 The height 6.7. One base is 3.6 km and the other base is unknown (x). The problem looks like 38.9= 6.7(3.6 + x). I then divided 6.7 into 38.9 to see what I would need to add to 3.6 to get the correct answer. I got 5.8. So, I took 3.6 away from it and got x=2.2. I

**I've corrected, but if this isn't correct, I don't know how to do it.

 

[JeffM]

2. The height of a trapezoid's right angle side is 5 in. Neither base is listed. Therefore, I assigned one base to be x. I assume the other base will be the same number as x in that one of the examples the teacher gave us was like that. The area is 60 in^2. I used A= h(b1 + b2). Therefore: 60 in^2= 5(x + x). Knowing that 12 x 5 = 60. I determined that x had to be 6?

**This problem seems to be missing data. Please review and correct. I have listed more information and corrected this problem.

3. The height of a trapezoid is x mi. B1 = 3.3 mi and B2 = 7.3 mi The area = 29.2 mi^2. Here is how I tried to work it: 29.2 mi=x(3.3+7.3)/2 Why did you divide by 2? Wouldn't it be A=H(b1+b2). Wouldn't that be 29.2 = x (3.3+7.3=10.6) or 10.6x 29.2=10.6x Divided each side by 10.6--
x=2.8 mi
** I've corrected my problem. Now is it correct? Incorrect - fix it by fixing the area equation and associated arithmetic. Check your answer by recalculating the area.

4. A=38.9 km^2 The height 6.7. One base is 3.6 km and the other base is unknown (x). The problem looks like 38.9= 6.7(3.6 + x). I then divided 6.7 into 38.9 to see what I would need to add to 3.6 to get the correct answer. I got 5.8. So, I took 3.6 away from it and got x=2.2. I

**I've corrected, but if this isn't correct, I don't know how to do it.

You did not remember the formula for the area of a trapezoid correctly. It is

$\displaystyle A = \dfrac{b_1 + b_2}{2} * h.$ That is where the 2 came from in problem 3. Using the wrong formula will cause errors over and over again. You are thinking generally along the right lines, but, in math, generally is not enough. You must pay attention to every detail.

See whether this site helps http://www.mathopenref.com/trapezoidarea.html

 

[Cindy Burgess]

Thank you!

WOW! I need to rework all the problems using that area formula! Thank you! You just saved my homework assignment grade. I like the website.

I checked out the website.

You did not remember the formula for the area of a trapezoid correctly. It is

$\displaystyle A = \dfrac{b_1 + b_2}{2} * h.$ That is where the 2 came from in problem 3. Using the wrong formula will cause errors over and over again. You are thinking generally along the right lines, but, in math, generally is not enough. You must pay attention to every detail.

See whether this site helps http://www.mathopenref.com/trapezoidarea.html