Answer:
17) 250 km²
18) never
19) sometimes
20) 288 in³
Explanation:
17)
this polygon can be seen as the combination of two shapes : a 16×13 rectangle on top, and a right-angled triangle at the bottom.
this triangle has the side lengths
15 km
(16 - 10) = 6 km
(27 - 13) = 14 km
the total area is the area of the rectangle plus the area of the triangle.
the area of the rectangle (length×width)
Ar = 16×13 = 208 km²
the area of the triangle (baseline×height/2)
since it is a right-angled triangle, we use one side of the 90 degree angle as baseline and the other as height
At = 6×14/2 = 3×14 = 42 km²
so the total area of the polygon
Ap = Ar + At = 208 + 42 = 250 km²
18) the first quadrant is the area between the right (positive) side of the x axis and the upper (positive) part of the y axis. all points here have always and only positive x and y values. never any negative ones.
19) when a point is on the x-axis, well, left of point 0 on the x -axis are only negative values of x. and right of point 0 of the x-axis are only positive values of x. so, for some of these points the x value is positive, and for some it is negative. therefore "sometimes".
20) the volume of a box is length×width×height.
V = 8×3×12 = 24×12 = 288 in³