Glencoe Math: Course 3, Volume 2
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Glencoe Math: Course 3, Volume 2 View details
2. Congruence
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Exercise 9 Page 526

Practice makes perfect

We are asked to determine whether the given statement is true or false.

If two figures are congruent, they have equal perimeters.

Let's consider two example congruent figures.

In congruent figures, corresponding sides are congruent.

The perimeter of a figure is the sum of the lengths of the sides of the figure. Perimeter ofABCDE = AB + BC + CD + DE + EA Notice that each side of FGHIJ is the same length as the corresponding side of ABCDE. Therefore, AB is equal to FG, BC is equal to GH, CD is equal to HI, DE is equal to IJ, and EA is equal to JF. AB + BC + CD + DE + EA = FG + GH + HI + IJ + JF The sums of the lengths of sides of both figures are equal. This means that the perimeters of the two figures are equal. Perimeter ofABCDE = Perimeter ofFGHIJ The same reasoning works for any pair of congruent figures. Therefore, any two congruent figures have equal perimeters and the statement is true.

We are given another statement and want to determine whether or not it is true.

If two figures have the same perimeter, they are congruent.

The perimeter of a figure is the sum of the lengths of the figure's sides. Let's consider an example figure.

The perimeter of this figure is 6* 4 = 24 inches. This number that this is the same as 3 * 8 inches, so a triangle with all sides 8 inches long would the same perimeter.

The square and the triangle have equal perimeters, but they are different shapes, so they are not congruent. Therefore, the statement is false.