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Finding Unknown Lengths in Similar Figures

Using Similar Figures. Course 2. Finding Unknown Lengths in Similar Figures. AC QS. AB QR. =. Write a proportion using corresponding sides. 14 w. 12 48. =. Substitute lengths of the sides. 12 · w = 48 · 14. Find the cross product. Multiply. 12 w = 672. 672 12. 12 w 12. =.

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Finding Unknown Lengths in Similar Figures

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  1. Using Similar Figures Course 2 Finding Unknown Lengths in Similar Figures AC QS AB QR = Write a proportion using corresponding sides. 14 w 12 48 = Substitute lengths of the sides. 12 · w = 48 · 14 Find the cross product. Multiply. 12w = 672 672 12 12w 12 = Divide each side by 12 to isolate the variable. w = 56 QR is 56 centimeters.

  2. Using Similar Figures Course 2 Insert Lesson Title Here Find the unknown length x Q R 10 cm B A 24 cm 12 cm D C T S AC QS AB QR = Write a proportion using corresponding sides. 10 x 12 24 Substitute lengths of the sides. = Find the cross product. 12 · x = 24 · 10 12x = 240 Multiply. 240 12 12x 12 Divide each side by 12 to isolate the variable. = x = 20 QR is 20 centimeters.

  3. Using Similar Figures Course 2 Measurement Application A volleyball court is a rectangle that is similar in shape to an Olympic-sized swimming pool. Find the length of the pool. Let l = the length of the pool. 9 25 18 l Write a proportion using corresponding side widths. = 9 ·l = 18 · 25 Find the cross products. Multiply. 9l = 450 9l 9 = 450 9 Divide each side by 9 to isolate the variable. l = 50 The pool is 50 meters long.

  4. Using Similar Figures Course 2 Insert Lesson Title Here The rectangle on the left is similar in shape to the rectangle on the right. Find the width of the right rectangle. 12 cm 6 cm 3 cm ? Let w = the width of the right rectangle. 6 12 3 w Write a proportion using corresponding side lengths. = 6 ·w = 12 · 3 Find the cross products. Multiply. 6w = 36 36 6 6w 6 = Divide each side by 6 to isolate the variable. w = 6 The right rectangle is 6 cm wide.

  5. Using Similar Figures Course 2 Using Indirect Measurement City officials want to know the height of a traffic signal. The traffic light casts a shadow that is 45 ft long. A stop sign casts a shadow that is 30 ft long. If the stop sign is 15 ft high, what is the height of the traffic light? Let x = the height of the traffic light. 30 45 15 x = Write a proportion. Find the cross product. 30 · x = 45 · 15 Multiply. 30 x = 675 30x 30 675 30 Divide each side by 30 to isolate the variable. = x = 22.5 The traffic light is 22.5 feet tall.

  6. Using Similar Figures Course 2 Insert Lesson Title Here The inside triangle is similar in shape to the outside triangle. Find the length of the base of the inside triangle. Let x = the base of the inside triangle. 8 2 12 x Write a proportion using corresponding side lengths. = 8 · x = 2 · 12 Find the cross products. Multiply. 8x = 24 8x 8 24 8 = Divide each side by 8 to isolate the variable. x = 3 The base of the inside triangle is 3 inches.

  7. Using Similar Figures Course 2 Insert Lesson Title Here Lesson Quiz Find the unknown length in each pair of similar figures. J 3. These two rectangular cakes are similar in shape. How long is the larger cake? A 144 cm 96 cm 1. x C 80 cm K 56 cm B 84 cm L 10 in. x = 120 cm x 6 in. 2. 9 in. 160 cm t 120 cm 72 cm 90 cm x = 15 inches t = 150 cm

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