AMC 8 Daily Practice - Perimeter Tricks

Complete problem set with solutions and individual problem pages

Problem 1 Easy

The following figure is a side view of a staircase. It is known that each step is 30 cm wide and 20 cm high. What is the perimeter of the side of this staircase in meters?

  • A.

    4

  • B.

    8

  • C.

    16

  • D.

    400

  • E.

    800

Answer:B

Through translation, it can be known that the length BC of the staircase in the figure is 30 \times 8 = 240 cm, and the height AB of the staircase is 20 \times 8 = 160 cm.

Therefore, the perimeter of the side of the staircase is 240 + 160 + (30 + 20) \times 8 = 800 \text{ cm}.

Note the unit conversion: 800 \text{ cm} = 8 \text{ m}.

Thus, the final answer is \boxed{8}m .

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Problem 2 Easy

Seven identical rectangles, each with a length of 5 cm and a width of 2 cm, are arranged as shown in the figure below. What is the perimeter of this figure in centimeters?

  • A.

    82

  • B.

    86

  • C.

    90

  • D.

    94

  • E.

    98

Answer:B

As shown in the figure, the perimeter of the combined figure can be calculated using the formula: \text{Perimeter} = 7 \times \text{(Perimeter of one rectangle)} - 6 \times \text{(Width of one rectangle)}.

Given that the length l = 5cm and width w = 2cm, the perimeter of one rectangle is 2 \times (5 + 2) = 14cm.

Substituting these values into the formula: \text{Perimeter} = 7 \times 14 - 6 \times 2 = 98 - 12 = 86 cm.

Thus, the perimeter of the figure is \boxed{86}cm.

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Problem 3 Easy

What is the perimeter of the following figure?

  • A.

    120

  • B.

    150

  • C.

    160

  • D.

    240

  • E.

    320

Answer:C

 

Starting from point A and walking clockwise around the figure, we mark the direction of movement and find that:

The sum of upward paths = the sum of downward paths = (15 +25) = 40m

The sum of rightward paths = the sum of leftward paths = 40m

Therefore, the perimeter of the figure is: (40 + 40) \times 2 = 160m.

Thus, the final answer is \boxed{160}m.

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Problem 4 Easy

A rectangle is divided into four pieces. Given that the perimeter of piece A is 8 cm, the perimeter of piece B is 30 cm, and the perimeter of piece D is 38 cm, what is the perimeter of the large rectangle?

  • A.

    42cm

  • B.

    44cm

  • C.

    46cm

  • D.

    48cm

  • E.

    50cm

Answer:C

Using the translation method, we know that:

The perimeter of the large rectangle = the perimeter of piece A + the perimeter of piece D, which is 8 + 38 = 46 cm.

Final answer: \boxed{46cm}.

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Problem 5 Easy

In the backyard, there is a rectangular flower bed with a square vegetable garden inside it. Emily wants to put a fence around its outer edge. What is the perimeter of the flower bed in feet?

  • A.

    70

  • B.

    72

  • C.

    74

  • D.

    76

  • E.

    78

Answer:B

The perimeter of the rectangle = AD + DE+EH + HA=AB + BC + CD + DE+EF + FG + GH + HA.

Since AB + BC = 20, EF + FG=16, and BC = DE = FG = HA, AB = GH, CD = EF, we can calculate the perimeter of the rectangle as follows:

The perimeter of the rectangle

=AB + BC+GH + HA + EF+FG + CD + DE

=(AB + CD)\times2+(EF + FG)\times2

=2\times20 + 2\times16=40 + 32=72

So the perimeter of the rectangular flower bed is 72 feet.

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Problem 6 Easy

In the diagram, all angles are right angles and the lengths of the sides are given in centimeters.Note the diagram is not drawn to scale. What is the length in X, in centimeters?

  • A.

    3

  • B.

    2.5

  • C.

    1.3

  • D.

    2

  • E.

    3.5

Answer:B

Using the translation method, we find that:

5 + 4 + 4 = 3 + 1.5 + 6 + X

Solving for X:

13 = 10.5 + X \Rightarrow X = 13 - 10.5 = 2.5

Thus, the length of X is 2.5cm.

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Problem 7 Easy

A puppy starts at point A, walks along the direction of AO, turns midway to walk parallel to OB, then turns again to walk parallel to AO, and continues this pattern until reaching point B, then returns to A along BA. Given that the perimeter of triangle AOB is 55 meters, how many meters does the puppy walk in total?

  • A.

    45

  • B.

    50

  • C.

    55

  • D.

    60

  • E.

    65

Answer:C

Using the translation method, we observe that the distance the puppy walks is exactly the perimeter of triangle AOB.

Therefore, the total distance the puppy walks is: 55 \text{ meters}

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Problem 8 Easy

A figure is formed by arranging 22 small pieces of paper of the same size as shown in the diagram. Given that the length of each small piece of paper is 15 centimeters, what is the total perimeter of the shaded parts in the figure?

  • A.

    15cm

  • B.

    20cm

  • C.

    45cm

  • D.

    60cm

  • E.

    75cm

Answer:D

As shown in the diagram, we can observe that 5 lengths =3 lengths +3 widths.

Therefore, 2 lengths =3 widths.

Given that the length is 15\text{ cm}, the width can be calculated as follows: \text{Width} = 15 \times 2 \div 3 = 10cm.

The perimeter of one shaded part is \text{length} - \text{width} = 15 - 10 = 5 cm.

Thus, the total perimeter of the shaded parts is: 5 \times 4 \times 3 = 60cm.

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