Perimeter of a Triangle Practice

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Question 2

Given the perimeter of a triangle is 18ft. Its side lengths are 5ft, 7ft and x ft. Find x.

Answer

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Select and check your answer...

A. 5 ft
B. 6 ft
C. 7 ft
D. 8 ft

Step by Step Solution

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    Step 1

    The picture below shows the triangle:

    a triangle with side lengths of 5ft, 7ft and x ft
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    Step 2

    We start with the formula for the perimeter of a triangle, P, as shown below.

    formula for the perimeter of a triangle
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    Step 3

    Since the values of the perimeter and the side lengths are given, we can substitute these values into the formula as shown:

    calculating the perimeter of a triangle
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    Step 4

    To find x, we need to remove 12. To do so, we add -12 to both sides of the equation:

    x is calculated as 6
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    Step 5

    Now, we have x = 6. Remember that, it is important to include the unit. Hence:

    x = 6ft
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    Step 6

    Therefore, the answer is B.

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