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Perimeter and area on the coordinate plane

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55191010
The graph shows rectangle \(ABCD\). Find its area.
Figure for problem 551910

Hints

- Read the coordinates of the rectangle's vertices from the graph. - Find the horizontal and vertical side lengths using coordinate differences. - Use the rectangle area formula once the side lengths are known.

Solution

1. The horizontal side length is \(6-1=5\) units. 2. The vertical side length is \(4-1=3\) units. 3. The area is \(5\cdot 3=15\) square units.

Answer

\(15\) square units
55191110
The graph shows right triangle \(ABC\). Find its area.
Figure for problem 551911

Hints

- Identify a base and a perpendicular height from the coordinate graph. - Horizontal and vertical coordinate differences give those two lengths directly. - Use the triangle area formula rather than the rectangle area formula.

Solution

1. \(\overline{AB}\) is a horizontal leg of length \(4\) units. 2. \(\overline{AC}\) is a vertical leg of length \(3\) units. 3. The area is \(\frac{1}{2}\cdot 4\cdot 3=6\) square units.

Answer

\(6\) square units
52415610
Quadrilateral \(PQRS\) is a rectangle. Three vertices are \(P(1, 1)\), \(Q(9, 1)\), and \(R(9, 5)\). 1. Find the coordinates of the fourth vertex \(S\). 2. One coordinate unit represents \(1\,\text{cm}\). Find the perimeter of the rectangle. 3. Find the area of the rectangle.

Hints

- Match x- and y-coordinates to complete the axis-aligned rectangle. - Find the two side lengths from coordinate differences before using either measurement formula. - Keep linear units for perimeter and square units for area.

Solution

1. Point \(S\) has the same x-coordinate as \(P\) and the same y-coordinate as \(R\), so \(S=(1, 5)\). 2. The side lengths are \(9-1=8\,\text{cm}\) and \(5-1=4\,\text{cm}\). The perimeter is \(2(8+4)=24\,\text{cm}\). 3. The area is \(8\,\text{cm}\cdot4\,\text{cm}=32\,\text{cm}^2\).

Answer

1. \(S=(1, 5)\) 2. \(24\,\text{cm}\) 3. \(32\,\text{cm}^2\)
54430710
A rectangular solution set is defined by \(x\ge0\), \(y\ge0\), \(x\le4\), and \(y\le3\). Find its area and perimeter, and state whether it is bounded.

Hints

- Read the horizontal and vertical side lengths from the coordinate bounds. - Use the rectangle formulas for area and perimeter. - A set is bounded when it cannot extend indefinitely in any direction.

Solution

1. The x-values run from \(0\) to \(4\), so the rectangle has width \(4\). 2. The y-values run from \(0\) to \(3\), so the rectangle has height \(3\). 3. Its area is \(4\cdot3=12\) square units, and its perimeter is \(2(4+3)=14\) units. 4. Both coordinates have lower and upper bounds, so the solution set is bounded.

Answer

The area is \(12\) square units, the perimeter is \(14\) units, and the solution set is bounded.
55092910
The graph shows triangle \(ABC\). Find its area in square units.
Figure for problem 550929

Hints

- Choose a side that makes the base length easy to read from the coordinates. - The height must be perpendicular to the chosen base. - Use the triangle area formula after finding the base and height.

Solution

1. From the graph, \(A=(1, 1)\), \(B=(7, 1)\), and \(C=(4, 5)\). 2. Segment \(\overline{AB}\) is a horizontal base of length \(7-1=6\) units. 3. The perpendicular height from \(C\) to line \(AB\) is \(5-1=4\) units. 4. The area is \(\frac{1}{2}\cdot 6\cdot 4=12\) square units.

Answer

\(12\) square units
55191210
The graph shows an L-shaped polygon \(ABCDEF\). Find its perimeter and area.
Figure for problem 551912

Hints

- Read each horizontal and vertical side length from coordinate differences on the graph. - Be sure the perimeter follows the inward notch as well as the outside boundary. - For area, compare the L-shape with a surrounding rectangle and identify the missing rectangular piece.

Solution

1. From the graph, the side lengths are \(AB=6\), \(BC=2\), \(CD=3\), \(DE=3\), \(EF=3\), and \(FA=5\) units. 2. The perimeter is \(6+2+3+3+3+5=22\) units. 3. For the area, view the figure as a \(6\times5\) outer rectangle with a \(3\times3\) rectangle removed. 4. The area is \(6\cdot5-3\cdot3=21\) square units.

Answer

Perimeter: \(22\) units Area: \(21\) square units
55491310
Rectangle \(ABCD\) has vertices \(A=(-1,2)\), \(B=(5,2)\), \(C=(5,y)\), and \(D=(-1,y)\), where \(y>2\). Its area is \(30\) square units. Find \(y\).

Hints

- Use the known x-coordinates to determine one side length. - Express the other side length using \(y\) and the given condition \(y>2\). - Set the product of the two side lengths equal to the stated area.

Solution

1. The horizontal side length is \(5-(-1)=6\) units. 2. Because \(y>2\), the vertical side length is \(y-2\) units. 3. Use the rectangle area: \(6(y-2)=30\). 4. Then \(y-2=5\), so \(y=7\).

Answer

\(y=7\)
55493010
Rectangle \(ABCD\) has vertices \(A=(-1,2)\), \(B=(5,2)\), \(C=(5,y)\), and \(D=(-1,y)\), where \(y>2\). Its area is \(30\) square units. Find \(y\).

Hints

- Use the known x-coordinates to determine one side length. - Express the other side length using \(y\) and the given condition \(y>2\). - Set the product of the two side lengths equal to the stated area.

Solution

1. The horizontal side length is \(5-(-1)=6\) units. 2. Because \(y>2\), the vertical side length is \(y-2\) units. 3. Use the rectangle area: \(6(y-2)=30\). 4. Then \(y-2=5\), so \(y=7\).

Answer

\(y=7\)
51297510
Consider the lines \(f(x) = x\), \(g(x) = -x\), and the horizontal line \(h(x) = c\), where \(c > 0\). The three lines enclose a triangle. a) Use the vertices to show that the area of the triangle is always \(A = c^2\). b) How does the area change if \(c\) is doubled? Explain without drawing a new graph.

Hints

- Express each vertex in terms of \(c\). - Which two vertices lie on the horizontal line \(y = c\)? - What happens to the square of a quantity when the quantity is doubled?

Solution

1. The lines \(f\) and \(g\) intersect where \(x = -x\), so \(x = 0\) and \(y = 0\). One vertex is \((0, 0)\). 2. The intersection of \(f\) and \(h\) satisfies \(x = c\), giving \((c, c)\). The intersection of \(g\) and \(h\) satisfies \(-x = c\), giving \((-c, c)\). 3. The horizontal base has length \(c - (-c) = 2c\), and the height from the origin to \(y = c\) is \(c\). 4. Therefore, \(A = \frac{1}{2} \cdot 2c \cdot c = c^2\). 5. If \(c\) is doubled, the new area is \((2c)^2 = 4c^2\), so the area is multiplied by \(4\).

Answer

a) The vertices are \((0, 0)\), \((c, c)\), and \((-c, c)\). The base is \(2c\) and the height is \(c\), so \(A = c^2\). b) The area quadruples because \((2c)^2 = 4c^2\).
51310110
The lines \(a: y=x+1\) and \(b: y=-0.5x+4\) are given. a) Find their intersection point \(S\) algebraically. b) Find the area of the triangle bounded by lines \(a\), \(b\), and the y-axis. c) Reflect the triangle from part b across the y-axis. Find the area of the kite formed by the original triangle and its reflection.

Hints

- Find where the two lines have the same y-value. - The two y-intercepts form one side of the triangle. - What is the horizontal distance from the intersection point to the y-axis? - How does reflection affect area?

Solution

a) Set the line equations equal: \(x+1=-0.5x+4\). Then \(1.5x=3\), so \(x=2\). Substitution gives \(y=3\), so \(S=(2, 3)\). b) The y-intercepts are \((0, 1)\) and \((0, 4)\), so the vertical base has length \(3\). The perpendicular distance from \(S(2, 3)\) to the y-axis is \(2\), so the area is \(A=\frac{1}{2}\cdot 3\cdot 2=3\) square units. c) Reflection preserves area. The kite consists of the original triangle and its reflected copy, so its area is \(2\cdot 3=6\) square units.

Answer

a) \(S=(2, 3)\) b) \(3\) square units c) \(6\) square units
51317810
Four lines enclose a parallelogram: \(f(x) = 2\) \(g(x) = -3\) \(h(x) = x + 1\) \(k(x) = x - 4\) Find the area of the enclosed parallelogram.

Hints

- Identify the pairs of parallel lines first. - Find the vertices by intersecting one line from each parallel pair. - What is the vertical distance between the two horizontal lines? - Use the parallelogram area formula once you know a base and its corresponding height.

Solution

1. Find the vertices from pairwise intersections. From \(2 = x + 1\), \(f\) and \(h\) meet at \((1, 2)\). From \(2 = x - 4\), \(f\) and \(k\) meet at \((6, 2)\). From \(-3 = x - 4\), \(g\) and \(k\) meet at \((1, -3)\). From \(-3 = x + 1\), \(g\) and \(h\) meet at \((-4, -3)\). 2. The horizontal side from \((1, 2)\) to \((6, 2)\) has length \(6 - 1 = 5\). 3. The perpendicular height is the vertical distance between \(y = 2\) and \(y = -3\), which is \(2 - (-3) = 5\). 4. Therefore, the area is \(A = 5 \cdot 5 = 25\) square units.

Answer

\(25\) square units
51322710
The functions \(f(x)=\frac{1}{2}x+1\) and \(g(x)=\frac{1}{2}x-2\) are given. a) Explain why the graphs of \(f\) and \(g\) are parallel. b) A third line is \(h(x)=-x+b\). It must intersect \(f\) at the point on \(f\) whose x-coordinate is \(2\). Find \(b\). c) The graphs of \(f\), \(h\), \(g\), and the y-axis bound a quadrilateral. Find its area.

Hints

- Compare the slopes and y-intercepts of \(f\) and \(g\). - Use the stated x-coordinate to locate the required intersection point of \(f\) and \(h\). - Find every vertex of the bounded quadrilateral before computing its area. - Choose a coordinate-area method that works for a non-axis-aligned quadrilateral.

Solution

1. Lines \(f\) and \(g\) both have slope \(\frac{1}{2}\) and have different y-intercepts, so they are distinct parallel lines. 2. At \(x=2\), \(f(2)=\frac{1}{2}\cdot2+1=2\). Since \(h\) passes through \((2,2)\), \(2=-2+b\), so \(b=4\) and \(h(x)=-x+4\). 3. The y-axis meets \(f\) at \((0,1)\) and \(g\) at \((0,-2)\). Line \(h\) meets \(f\) at \((2,2)\). 4. To find the remaining vertex, solve \(-x+4=\frac{1}{2}x-2\). This gives \(x=4\) and \(y=0\), so the fourth vertex is \((4,0)\). 5. Using the vertices in order \((0,1)\), \((2,2)\), \((4,0)\), \((0,-2)\), the shoelace formula gives area \(\frac{1}{2}|-8-10|=9\) square units.

Answer

a) They are parallel because both have slope \(\frac{1}{2}\) and different y-intercepts. b) \(b=4\) c) \(9\) square units
51414510
A line passes through \(A(-2, 3)\) and \(B(4, 0)\). Together with the coordinate axes, the line encloses a triangular region. Find the line's intercepts with the axes and the area of the triangle.

Hints

- One of the given points already lies on a coordinate axis. Which one? - How can you find a line equation from two points? - What shape do the two intercepts and the origin form? - How do you find the area of a right triangle?

Solution

1. The slope through \(A\) and \(B\) is \(\frac{0 - 3}{4 - (-2)} = -\frac{1}{2}\). 2. Since \(B(4, 0)\) lies on the x-axis, the x-intercept is \((4, 0)\). 3. Write the line as \(y = -0.5x + b\). Using \((4, 0)\), \(0 = -0.5 \cdot 4 + b\), so \(b = 2\). The y-intercept is \((0, 2)\). 4. The axes and the line form a right triangle with legs of lengths \(4\) and \(2\). Its area is \(\frac{1}{2} \cdot 4 \cdot 2 = 4\) square units.

Answer

The intercepts are \((4, 0)\) and \((0, 2)\). The area is \(4\) square units.
55093010
The graph shows quadrilateral \(ABCD\). Find its perimeter in units.
Figure for problem 550930

Hints

- Read the four vertex coordinates in order around the quadrilateral. - Use the distance formula because none of the sides is horizontal or vertical. - Add the four side lengths only after finding each one.

Solution

1. From the graph, \(A=(0, 0)\), \(B=(4, 3)\), \(C=(-2, 11)\), and \(D=(-6, 8)\). 2. \(AB=\sqrt{4^2+3^2}=5\) and \(BC=\sqrt{(-6)^2+8^2}=10\). 3. Likewise, \(CD=\sqrt{(-4)^2+(-3)^2}=5\) and \(DA=\sqrt{6^2+(-8)^2}=10\). 4. The perimeter is \(5+10+5+10=30\) units.

Answer

\(30\) units
55491210
The graph shows rectangle \(ABCD\). None of its sides is horizontal or vertical. a) Use the distance formula to find the exact lengths \(AB\) and \(BC\). b) Use those side lengths to find the area of the rectangle in square units.
Figure for problem 554912

Hints

- Read the coordinates of \(A\), \(B\), and \(C\) from the graph. - Apply the distance formula separately to the two adjacent oblique sides requested in part a). - Use the exact side lengths from part a) in the rectangle area formula.

Solution

1. From the graph, \(A=(0,0)\), \(B=(3,2)\), \(C=(-1,8)\), and \(D=(-4,6)\). 2. \(AB=\sqrt{(3-0)^2+(2-0)^2}=\sqrt{13}\). 3. \(BC=\sqrt{(-1-3)^2+(8-2)^2}=\sqrt{52}=2\sqrt{13}\). 4. The rectangle area is \(AB\cdot BC=\sqrt{13}\cdot2\sqrt{13}=26\) square units.

Answer

a) \(AB=\sqrt{13}\) units; \(BC=2\sqrt{13}\) units b) \(26\) square units
55492910
The graph shows rectangle \(ABCD\). None of its sides is horizontal or vertical. a) Use the distance formula to find the exact lengths \(AB\) and \(BC\). b) Use those side lengths to find the area of the rectangle in square units.
Figure for problem 554929

Hints

- Read the coordinates of \(A\), \(B\), and \(C\) from the graph. - Apply the distance formula separately to the two adjacent oblique sides requested in part a). - Use the exact side lengths from part a) in the rectangle area formula.

Solution

1. From the graph, \(A=(0,0)\), \(B=(3,2)\), \(C=(-1,8)\), and \(D=(-4,6)\). 2. \(AB=\sqrt{(3-0)^2+(2-0)^2}=\sqrt{13}\). 3. \(BC=\sqrt{(-1-3)^2+(8-2)^2}=\sqrt{52}=2\sqrt{13}\). 4. The rectangle area is \(AB\cdot BC=\sqrt{13}\cdot2\sqrt{13}=26\) square units.

Answer

a) \(AB=\sqrt{13}\) units; \(BC=2\sqrt{13}\) units b) \(26\) square units

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