ISEE Middle Level Math : Lines

Study concepts, example questions & explanations for ISEE Middle Level Math

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Example Questions

Example Question #11 : Lines

Rec

The coordinates of \(\displaystyle DB\) on the rectangle are \(\displaystyle D (5,2)\) and \(\displaystyle B (7,-3)\). Find the length of the diagonal.

Possible Answers:

\(\displaystyle d \approx 5.4\)

\(\displaystyle d\approx 6.4\)

\(\displaystyle d \approx 4.4\)

\(\displaystyle d\approx 7.4\)

Correct answer:

\(\displaystyle d \approx 5.4\)

Explanation:

A rectangle has two diagonals with the same length. Therefore, use the distance formula to calculate the distance.

\(\displaystyle d = \sqrt{(x_{2} - x_{1})^{2} + (y_{2}- y_{1})^{2}\)

 \(\displaystyle (7-5)^{2} = 2^{2} = 4\)

\(\displaystyle (-3-2)^{2} = -5^{2} = 25\)

\(\displaystyle \sqrt{4+25}\)

\(\displaystyle \sqrt{29} \approx 5.4\)

\(\displaystyle d \approx 5.4\)

Example Question #81 : Geometry

If a circle has a radius of \(\displaystyle 8cm\), what would be the length of the longest line drawn within that circle?

Possible Answers:

\(\displaystyle 15cm\)

\(\displaystyle 10cm\)

\(\displaystyle 4cm\)

\(\displaystyle 16cm\)

Correct answer:

\(\displaystyle 16cm\)

Explanation:

The diameter of the circle would be the longest line that can be drawn within that circle.

Because radius is half of the diameter, the diameter is calculated by multiplying the radius of the circle by two.

If the radius is \(\displaystyle 8cm\),  then the diameter is \(\displaystyle 8m \times 2 = 16m\)

 

Example Question #82 : Geometry

A ladder is leaning on a wall.  It is \(\displaystyle 16ft\) ft long.  The bottom of the ladder is \(\displaystyle 10ft\) from the base.  How far up the wall is the top of the ladder?

Possible Answers:

\(\displaystyle \approx 14ft\)

\(\displaystyle \approx13.5ft\)

\(\displaystyle \approx11.5ft\)

\(\displaystyle \approx 12.5ft\)

Correct answer:

\(\displaystyle \approx 12.5ft\)

Explanation:

The Pythagorean Theorem states that:

\(\displaystyle a^{2} +b^{2} = c^{2}\)

With \(\displaystyle a\) and \(\displaystyle b\) representing the measurement of the legs and \(\displaystyle C\) representing the hypotenuse.

\(\displaystyle 10^{2} +b^{2} = 16^{2}\)

\(\displaystyle 100 + b^{2} = 256\)

\(\displaystyle (100-100) + b^{2} = 256-100\)

\(\displaystyle b^{2} = 156\)

\(\displaystyle \sqrt{b^{2}} = \sqrt{156}\)

\(\displaystyle b\approx 12.5ft\)

Example Question #83 : Geometry

What is the perimeter of a right triangle if the hypotenuse is \(\displaystyle 15cm\) and the measurement of one of its legs is \(\displaystyle 9cm?\)

Possible Answers:

\(\displaystyle 12cm\)

\(\displaystyle 39cm\)

\(\displaystyle 36cm\)

\(\displaystyle 33cm\)

Correct answer:

\(\displaystyle 36cm\)

Explanation:

First, use the Pythagorean Theorem to get the measurement of the other leg.

\(\displaystyle a^{2} +b^{2} =c^{2}\)

\(\displaystyle 9^{2} + b^{2} =15^{2}\)

\(\displaystyle 81 + b^{2} = 225\)

\(\displaystyle (81-81) + b^{2} = 225-81\)

\(\displaystyle b^{2} = 144\)

\(\displaystyle b = 12cm\)

To get the perimeter of the triangle, add the measurements of each of the three sides.

\(\displaystyle 9 + 15 + 12 = 36cm\)

Example Question #84 : Geometry

A line has endpoints \(\displaystyle (7,9)\) and \(\displaystyle (1,1).\)  What is the distance of the line?

Possible Answers:

\(\displaystyle d = 10\)

\(\displaystyle d = 8\)

\(\displaystyle d = 12\)

\(\displaystyle d = 14\)

Correct answer:

\(\displaystyle d = 10\)

Explanation:

Use the distance formula

\(\displaystyle d = \sqrt{(x_{2} - x_{1})^{2} + (y_{2}- y_{1})^{2}\)

\(\displaystyle d=\sqrt{(7-1)^{2} + (9-1)^{2}}\)

\(\displaystyle d=\sqrt{36+64}\)

\(\displaystyle d = \sqrt{100}\)

\(\displaystyle d = 10\)

Example Question #82 : Plane Geometry

Line \(\displaystyle AB\) has a length of \(\displaystyle 80cm.\)  It is bisected at point \(\displaystyle C\), and the resulting segment \(\displaystyle AC\)is bisected again at point \(\displaystyle D.\)  What is the length of line segment \(\displaystyle AD?\)

Possible Answers:

\(\displaystyle 40cm\)

\(\displaystyle 20cm\)

\(\displaystyle 30cm\)

\(\displaystyle 50cm\)

Correct answer:

\(\displaystyle 20cm\)

Explanation:

First, write each portion of the statement in mathematical terms.

\(\displaystyle AC =\frac{1}{2} AB\)

Since AB=80 we will substitute that into the equation.

\(\displaystyle AC =\frac{1}{2} (80)\)

\(\displaystyle AC = 40\)

Now that we know AC we can calculate AD as follows.

\(\displaystyle AD = \frac{1}{2} AC\)

\(\displaystyle AD = \frac{1}{2}(40)\)

\(\displaystyle AD = 20cm\)

Example Question #86 : Geometry

The point \(\displaystyle (2,-2)\) lies on a circle. What is the approximate length of the radius of the circle if the center is \(\displaystyle (3,-5) ?\)

Possible Answers:

\(\displaystyle d\approx5\)

\(\displaystyle d=\sqrt{10}\)

\(\displaystyle d\approx 7\)

\(\displaystyle d=\sqrt{5}\)

Correct answer:

\(\displaystyle d=\sqrt{10}\)

Explanation:

Because the radius is the distance from center to any point on a circle, the distance formula is used to find the measurement of the radius.

\(\displaystyle d = \sqrt{(x_{2} - x_{1})^{2} + (y_{2}- y_{1})^{2}\)

\(\displaystyle d = \sqrt{(3-2)^{2} + (-5--2)^{2}\)

\(\displaystyle 1^{2} = 1\times1 = 1\)

\(\displaystyle -3^{2} = -3\times -3 = 9\)

\(\displaystyle d = \sqrt{1+9}\)

\(\displaystyle d =\sqrt{10}\)

Example Question #87 : Geometry

If the diameter of a circle is \(\displaystyle 12cm\), then what is \(\displaystyle \frac{1}{3}\) of the circle's radius?

Possible Answers:

\(\displaystyle 8cm\)

\(\displaystyle 2cm\)

\(\displaystyle 4cm\)

\(\displaystyle 10cm\)

Correct answer:

\(\displaystyle 2cm\)

Explanation:

Radius is \(\displaystyle \frac{1}{2}\) of the diameter.

If the diameter is \(\displaystyle 12cm\), then the radius is \(\displaystyle 6m.\)

\(\displaystyle \frac{1}{2}\cdot \frac{12}{1}=\frac{12}{2}=\frac{2\cdot6}{2}=6\)

Therefore

\(\displaystyle \frac{1}{3}\) of \(\displaystyle 6cm\) is,

\(\displaystyle \frac{1}{3}\cdot \frac{6}{1}=\frac{6}{3}=\frac{3\cdot 2}{3}=2cm\).

Example Question #82 : Plane Geometry

Find the slope of a line that passes through \(\displaystyle A (-5,-1)\) and \(\displaystyle B (3,-1)\).

Possible Answers:

The slope is undefined.

\(\displaystyle m = 8\)

\(\displaystyle m = -1\)

\(\displaystyle m = 0\)

Correct answer:

\(\displaystyle m = 0\)

Explanation:

Use the slope formula to solve:

\(\displaystyle m = \frac{y_{2} -y_{1}}{x_{2} - x_{1}}\)

Given the following points.

\(\displaystyle A (-5,-1)=(x_1,y_1)\)

\(\displaystyle B (3,-1)=(x_2,y_2)\)

The slope can be calculated as follows.

\(\displaystyle m = \frac{-1 - (-1)}{3- (-5)}\)

\(\displaystyle m = \frac{0}{8}\)

\(\displaystyle m = 0\)

Because the \(\displaystyle y\) coordinates were the same for points A and B, this would form a horizontal line.  The slope of any horizontal line is \(\displaystyle 0.\)

Example Question #89 : Geometry

Find the length of a line from the point \(\displaystyle (9,14)\) to the point \(\displaystyle (-12,36)\).

Possible Answers:

\(\displaystyle 30.4\)

\(\displaystyle 22\)

\(\displaystyle 21\)

\(\displaystyle 34\)

Correct answer:

\(\displaystyle 30.4\)

Explanation:

Find the length of a line from the point \(\displaystyle (9,14)\) to the point \(\displaystyle (-12,36)\).

To find this distance, we need to use distance formula (which is really similar to Pythagorean Theorem)

Distance formula is as follows

\(\displaystyle d=\sqrt{(x_1-x_2)^2+(y_1-y_2)^2}\)

Where our x's and y's come from our ordered pairs.

So, let's plug and chug

\(\displaystyle d=\sqrt{(9--12)^2+(14-36)^2}\)

Simplify

\(\displaystyle d=\sqrt{(21)^2+(-22)^2}\)

\(\displaystyle d=\sqrt{441+484}=\sqrt{925}\approx30.4\)

So our answer is 30.4

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