Examples with solutions for Perimeter of a Trapezoid: Calculate The Missing Side based on the formula

Exercise #1

The perimeter of the trapezoid in the diagram is 25 cm. Calculate the missing side.

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Video Solution

Step-by-Step Solution

We replace the data in the formula to find the perimeter:

25=4+7+11+x 25=4+7+11+x

25=22+x 25=22+x

2522=x 25-22=x

3=x 3=x

Answer

3 3 cm

Exercise #2

The perimeter of the trapezoid below is 30 cm. Calculate the length of the missing side.

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Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the given information
  • Step 2: Apply the perimeter formula
  • Step 3: Solve for the missing side

Now, let’s work through each step:

Step 1: The problem gives us a trapezoid with a perimeter of 30 cm and known side lengths of 8 cm, 4 cm, and 12 cm.
We let the missing side be x x cm.

Step 2: Use the perimeter formula for a trapezoid:

30=8+4+12+x 30 = 8 + 4 + 12 + x

Step 3: Combine the known side lengths:

30=24+x 30 = 24 + x

Solve for x x :

x=3024 x = 30 - 24 x=6 x = 6

Therefore, the length of the missing side is 6 cm.

Answer

6 cm

Exercise #3

What is the length of side AD given that the perimeter of the trapezoid is equal to 42 cm?

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Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the given perimeter and side lengths.
  • Step 2: Use the perimeter formula for a trapezoid.
  • Step 3: Solve for the missing side AD AD .

Let's begin:

Step 1: We know that the perimeter P=42 P = 42 cm. The other sides are AB=14 AB = 14 cm, BC=7 BC = 7 cm, and CD=12 CD = 12 cm.

Step 2: The formula for the perimeter is:

P=AB+BC+CD+AD P = AB + BC + CD + AD

Substituting in the known values:

42=14+7+12+AD 42 = 14 + 7 + 12 + AD

Step 3: Simplify the equation to find AD AD :

42=33+AD 42 = 33 + AD

Subtract 33 from both sides:

AD=4233 AD = 42 - 33

AD=9 AD = 9

Therefore, the length of side AD AD is 9 cm \textbf{9 cm} .

Answer

9

Exercise #4

Below is an isosceles trapezoid with a perimeter of 4X+2Y.

Calculate the lengths of the missing sides.

XXX3X3X3X

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Understand the properties of an isosceles trapezoid.
  • Step 2: Use the given information to set up equations for the perimeter.
  • Step 3: Solve the equations to find the missing side length.

Now, let's work through each step:

Step 1: An isosceles trapezoid has two parallel sides and two non-parallel sides that are equal in length. Here, the lengths of the parallel sides are given as XX and 3X3X. Therefore, the non-parallel sides (legs) must each be YY.

Step 2: According to the problem, the perimeter of the trapezoid is 4X+2Y4X + 2Y. The perimeter can also be expressed as the sum of all sides: X+3X+Y+YX + 3X + Y + Y.

So we write the equation:
X+3X+Y+Y=4X+2YX + 3X + Y + Y = 4X + 2Y

Simplify the equation:
4X+2Y=4X+2Y4X + 2Y = 4X + 2Y

This indicates that the setup is already balanced. Thus, the lengths of the missing sides (non-parallel sides) are each YY.

Therefore, the solution to the problem is Y Y .

Answer

Y

Exercise #5

Calculate X in the trapezoid below.

Perimeter = P

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Step-by-Step Solution

To solve this problem, we'll utilize the formula for the perimeter of a trapezoid.

The formula for the perimeter is given by:

  • P=a+b+c+d P = a + b + c + d

From the problem, we know:

  • The perimeter P P is 36.
  • The side lengths are 13, 12, and 5, with the unknown side as x x .

Plug these into the formula:

36=13+12+5+x 36 = 13 + 12 + 5 + x

Combine the known side lengths:

36=30+x 36 = 30 + x

To isolate x x , subtract 30 from both sides:

x=3630 x = 36 - 30

Calculate the result:

x=6 x = 6

Therefore, the length of the missing side x x is 6.

Thus, the correct answer is choice 2, corresponding to x=6 x = 6 .

Answer

6

Exercise #6

The perimeter of the trapezoid in the drawing is 34 cm. What is the length of the missing base?

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Video Solution

Step-by-Step Solution

To solve for the missing base of the trapezoid, follow these steps:

  • Identify given values: Perimeter P=34cm P = 34 \, \text{cm} , base 1 a=14cm a = 14 \, \text{cm} , leg 1 c=10cm c = 10 \, \text{cm} , leg 2 d=12cm d = 12 \, \text{cm} .
  • Set up the equation for the perimeter: P=a+b+c+d=34 P = a + b + c + d = 34 Substitute known values: 14+b+10+12=34 14 + b + 10 + 12 = 34
  • Simplify the equation: 36+b=34 36 + b = 34
  • Solve for b b : b=3436=2 b = 34 - 36 = -2

Since a side length cannot be negative, this trapezoid is impossible with these dimensions.

The correct choice is This trapeze is not possible.

Answer

This trapeze is not possible.

Exercise #7

Calculate the length of the second base given that the perimeter of the trapezoid in the drawing is 300% of the length of the base.

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Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Calculate the total perimeter as 300% of the known base 1717.
  • Step 2: Use the perimeter formula to isolate the unknown base.
  • Step 3: Solve for the unknown base.

Now, let's work through each step:
Step 1: Given that the base 1717 is part of the perimeter calculation and that the perimeter is 300% of this base, we have: P=3×17=51 P = 3 \times 17 = 51

Step 2: Using the perimeter formula for a trapezoid P=a+b+c+dP = a + b + c + d, where a=17a = 17, c=8c = 8, d=12d = 12, and bb is the unknown base, we have: 51=17+8+12+b 51 = 17 + 8 + 12 + b

Step 3: Solve for the unknown base bb: 51=37+b 51 = 37 + b b=5137 b = 51 - 37 b=14 b = 14

Therefore, the length of the second base of the trapezoid is 14 14 .

Answer

14

Exercise #8

Given an isosceles trapezoid whose perimeter 3X

Find the length of the short base

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Video Solution

Answer

213x12 2\frac{1}{3}x-12

Exercise #9

The area of the isosceles trapezoid below is 43 cm².

How long are the missing sides?

131313242424

Video Solution

Answer

3 3 cm

Exercise #10

The perimeter of a trapezoid is 3 times the length of its long base. Work out the length of the missing side.

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Video Solution

Answer

9