What is the value of 3ab+5b-6 when a=-1 and b=3? A.0 B.6 C.18 D.24
2 answers:
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Answer:
The area and the perimeter of the picture are:
- <u>Area = 160 cm^2</u>
- <u>Perimeter = 67.31 cm</u>
Step-by-step explanation:
To find the area of that figure, you can find the area how if it was a rectangle and next subtract the area of the triangle in the upper part. The area of a rectangle could be found by the next formula:
- Area of a rectangle = base * height
As you can see in the picture, the base is 16 cm and the height is 12 cm, then we replace in the formula:
- Area of a rectangle = 16 cm * 12 cm
- Area of a rectangle = 192 cm^2
Now, we calculate the area of the triangle to subtract to the area we found and obtain the real area, the formula to obtain the area of a triangle is:
- Area of a triangle = (base * height) / 2
The height of the triangle is 8 cm, and the base is 8 cm too, because you subtract to the base of the rectangle (16 cm) the measurements in the upper part (16 - 4 - 4 = 8), Now, we replace in the formula:
- Area of a triangle = (8 cm * 8 cm) / 2
- Area of a triangle = (64 cm^2) / 2
- Area of a triangle = 32 cm^2
We subtract to the found area:
- Area of the picture = 192 cm^2 - 32 cm^2
- <u>Area of the picture = 160 cm^2</u>
To find the perimeter, you must add all the sides of the picture, but, as you can see, there is a side that doesn't have the measurent, this is the hypotenuse of the triangle used before, but how we know the other sides, we can use Pythagorean theorem:
Where:
- a = Opposite leg (8 cm)
- b = Adjacent leg (8 cm)
So, we replace in the theorem:
(and we clear c)
-
- c = 11.3137085 cm
- c ≅ 11.31 cm
At last, we add all the sides of the picture begining by the base and going by the left side:
- Perimeter of the picture = 16 cm + 12 cm + 4 cm + 11.31 cm + 8 cm + 4 cm + 12 cm
- <u>Perimeter of the picture = 67.31 cm approximately</u>.