How to find the perimeter of an equilateral triangle - ISEE Upper Level Quantitative Reasoning

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Question

Refer to the above figure. The shaded region is a semicircle with area $16 \pi$ . Give the perimeter of $\bigtriangleup ABC$ .

Answer

Given the radius of a semicircle, its area can be calculated using the formula

$A = \frac{1}{2} \pi r ^{2}$ .

Substituting $A = 16 \pi$ :

$\frac{1}{2} \pi r ^{2} = 16 \pi$

$\frac{2}{\pi} \cdot \frac{1}{2} \pi r ^{2} = \frac{2}{\pi} \cdot 16 \pi$

$r ^{2} = 32$

$r = \sqrt{32} = \sqrt{16} \cdot \sqrt{2} = 4\sqrt{2}$

The diameter of this semicircle is twice this, which is $d = 2 \cdot 4\sqrt{2} = 8 \sqrt{2}$ ; this is also the length of $\overline{BC}$ .

$\bigtriangleup ABC$ has two angles of degree measure 60; its third angle must also have measure 60, making $\bigtriangleup ABC$ an equilateral triangle with sidelength $s = 8 \sqrt{2}$ . Its perimeter is three times this, or $3 \cdot 8 \sqrt{2} = 24 \sqrt{2}$

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Question

Find the perimeter of an equilateral triangle with a base of length 8cm.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle

Now, we know the base of the triangle is 8cm. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 8cm.

Knowing this, we can substitute into the formula. We get

$P = 8\text{cm} + 8\text{cm} + 8\text{cm}$

$P = 24\text{cm}$

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Question

Find the perimeter of an equilateral triangle with a base of 21in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle has a length of 21in. Because it is an equilateral triangle, all lengths are the same. Therefore, all lengths are 21in.

Knowing this, we can substitute into the formula. We get

$P = 21\text{in} +21\text{in} +21\text{in}$

$P = 63\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 23in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle has a length of 23in. Because it is an equilateral triangle, all lengths are the same. Therefore, all lengths are 23in.

Knowing this, we can substitute into the formula. We get

$P = 23\text{in} +23\text{in} +23\text{in}$

$P = 69\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 22in.

Answer

An equilateral triangle has 3 equal sides. So, we will use the following formula:

where a is the length of one side of the triangle.

Now, we know the base of the triangle is 22in. Because all sides are equal, all sides are 22in. So, we can substitute into the formula:

$P = 3 \cdot 22\text{in}$

$P = 66\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 19in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle is 19in. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 19in. So, we get

$P = 19\text{in} + 19\text{in} + 19\text{in}$

$P = 57\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 14in.

Answer

An equilateral triangle has 3 equal sides. To find the perimeter of an equilateral triangle, we will use the following formula:

where a is the length of one side of the triangle.

Now, we know the base of the equilateral triangle is 14in. So, we get

$P = 3 \cdot 14\text{in}$

$P = 42\text{in}$

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Question

Refer to the above figure. The shaded region is a semicircle with area $16 \pi$ . Give the perimeter of $\bigtriangleup ABC$ .

Answer

Given the radius of a semicircle, its area can be calculated using the formula

$A = \frac{1}{2} \pi r ^{2}$ .

Substituting $A = 16 \pi$ :

$\frac{1}{2} \pi r ^{2} = 16 \pi$

$\frac{2}{\pi} \cdot \frac{1}{2} \pi r ^{2} = \frac{2}{\pi} \cdot 16 \pi$

$r ^{2} = 32$

$r = \sqrt{32} = \sqrt{16} \cdot \sqrt{2} = 4\sqrt{2}$

The diameter of this semicircle is twice this, which is $d = 2 \cdot 4\sqrt{2} = 8 \sqrt{2}$ ; this is also the length of $\overline{BC}$ .

$\bigtriangleup ABC$ has two angles of degree measure 60; its third angle must also have measure 60, making $\bigtriangleup ABC$ an equilateral triangle with sidelength $s = 8 \sqrt{2}$ . Its perimeter is three times this, or $3 \cdot 8 \sqrt{2} = 24 \sqrt{2}$

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Question

Find the perimeter of an equilateral triangle with a base of length 8cm.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle

Now, we know the base of the triangle is 8cm. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 8cm.

Knowing this, we can substitute into the formula. We get

$P = 8\text{cm} + 8\text{cm} + 8\text{cm}$

$P = 24\text{cm}$

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Question

Find the perimeter of an equilateral triangle with a base of 21in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle has a length of 21in. Because it is an equilateral triangle, all lengths are the same. Therefore, all lengths are 21in.

Knowing this, we can substitute into the formula. We get

$P = 21\text{in} +21\text{in} +21\text{in}$

$P = 63\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 23in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle has a length of 23in. Because it is an equilateral triangle, all lengths are the same. Therefore, all lengths are 23in.

Knowing this, we can substitute into the formula. We get

$P = 23\text{in} +23\text{in} +23\text{in}$

$P = 69\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 22in.

Answer

An equilateral triangle has 3 equal sides. So, we will use the following formula:

where a is the length of one side of the triangle.

Now, we know the base of the triangle is 22in. Because all sides are equal, all sides are 22in. So, we can substitute into the formula:

$P = 3 \cdot 22\text{in}$

$P = 66\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 19in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle is 19in. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 19in. So, we get

$P = 19\text{in} + 19\text{in} + 19\text{in}$

$P = 57\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 14in.

Answer

An equilateral triangle has 3 equal sides. To find the perimeter of an equilateral triangle, we will use the following formula:

where a is the length of one side of the triangle.

Now, we know the base of the equilateral triangle is 14in. So, we get

$P = 3 \cdot 14\text{in}$

$P = 42\text{in}$

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Question

Refer to the above figure. The shaded region is a semicircle with area $16 \pi$ . Give the perimeter of $\bigtriangleup ABC$ .

Answer

Given the radius of a semicircle, its area can be calculated using the formula

$A = \frac{1}{2} \pi r ^{2}$ .

Substituting $A = 16 \pi$ :

$\frac{1}{2} \pi r ^{2} = 16 \pi$

$\frac{2}{\pi} \cdot \frac{1}{2} \pi r ^{2} = \frac{2}{\pi} \cdot 16 \pi$

$r ^{2} = 32$

$r = \sqrt{32} = \sqrt{16} \cdot \sqrt{2} = 4\sqrt{2}$

The diameter of this semicircle is twice this, which is $d = 2 \cdot 4\sqrt{2} = 8 \sqrt{2}$ ; this is also the length of $\overline{BC}$ .

$\bigtriangleup ABC$ has two angles of degree measure 60; its third angle must also have measure 60, making $\bigtriangleup ABC$ an equilateral triangle with sidelength $s = 8 \sqrt{2}$ . Its perimeter is three times this, or $3 \cdot 8 \sqrt{2} = 24 \sqrt{2}$

Compare your answer with the correct one above

Question

Find the perimeter of an equilateral triangle with a base of length 8cm.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle

Now, we know the base of the triangle is 8cm. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 8cm.

Knowing this, we can substitute into the formula. We get

$P = 8\text{cm} + 8\text{cm} + 8\text{cm}$

$P = 24\text{cm}$

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Question

Find the perimeter of an equilateral triangle with a base of 21in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle has a length of 21in. Because it is an equilateral triangle, all lengths are the same. Therefore, all lengths are 21in.

Knowing this, we can substitute into the formula. We get

$P = 21\text{in} +21\text{in} +21\text{in}$

$P = 63\text{in}$

Compare your answer with the correct one above

Question

Find the perimeter of an equilateral triangle with a base of 23in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle has a length of 23in. Because it is an equilateral triangle, all lengths are the same. Therefore, all lengths are 23in.

Knowing this, we can substitute into the formula. We get

$P = 23\text{in} +23\text{in} +23\text{in}$

$P = 69\text{in}$

Compare your answer with the correct one above

Question

Find the perimeter of an equilateral triangle with a base of 22in.

Answer

An equilateral triangle has 3 equal sides. So, we will use the following formula:

where a is the length of one side of the triangle.

Now, we know the base of the triangle is 22in. Because all sides are equal, all sides are 22in. So, we can substitute into the formula:

$P = 3 \cdot 22\text{in}$

$P = 66\text{in}$

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Question

Find the perimeter of an equilateral triangle with a base of 19in.

Answer

To find the perimeter of a triangle, we will use the following formula:

where a, b, and c are the lengths of the sides of the triangle.

Now, we know the base of the triangle is 19in. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 19in. So, we get

$P = 19\text{in} + 19\text{in} + 19\text{in}$

$P = 57\text{in}$

Compare your answer with the correct one above

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