Step-by-step explanation:
it is really not complicated. we only need to type the numbers into the calculator.
so, what's the problem ? you don't know what a perimeter is ? it is the circumference, the total way you have to go when waking all around the figure.
you don't know the formulas for the areas of specific figures ?
let's start :
a)
the area of a rectangle is length×width. I hope you know this at least since first grade.
the important thing here is : the result is in² and not just in. it means an area counts the little squares that fill that area.
A = 30×8 = 240 in²
the perimeter, as explained, is the whole way around it. so, in the end, as you can easily see, we would have to go 2 times the long side and 2 times the short side.
the result is in (just a length, a distance not an area, not a cube, ...).
P = 2×30 + 2×8 = 60 + 16 = 76 in
b)
the area of a triangle is
baseline × height / 2
in this case (a right-angled triangle) we can assume one of the sides enclosing the 90 degree angle as baseline and the other as height (since there is already a 90 degree angle between them).
and again, the result is ft². we could express it also e.g. as in², but since the basic measures are in ft, it makes it better understandable to use ft².
A = 12×5/2 = 6×5 = 30 ft²
the perimeter is even easier than for the rectangle, as we have one side less to count.
and as before, we stay with ft.
P = 12 + 13 + 5 = 30 ft
c)
this is the only more special case.
but it is still easy.
the area is baseline × height.
and our unit of measurement here is cm, so the result will be cm².
A = 10×2 = 20 cm²
the perimeter is the same principle as with a regular rectangle, as the angles don't matter. only the side lengths matter.
so, again, while waking around it, we have to pass 2 times the long side and 2 times the short side.
and the result is a length, a distance again, so, it is cm.
P = 2×10 + 2×4 = 20 + 8 = 28 cm
