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### Transcript of Congruent and similar shapes Congruent shapes Similar shapes

• Congruent and similar shapesCongruent shapesSimilar shapes

• Congruent shapes

• 1. Which of these shapes are congruent to the yellow one?25431768AnswersHintsStart page

• Congruent shapes are all shown in yellow were you right?5431768Start page2

• What makes a pair of shapes congruent?Same anglesSame side lengthsCan be rotated or a mirror imageA cut-out of one shape will always fit exactly over the otherClick the green box if you want to go back to the first congruent shapes question page.

Question pageStart page

• 2. Which of these shapes are congruent to the yellow one?AnswersStart page251346789

• Congruent shapes are all shown in yellow were you right?Start page251

• Similar shapes

• Which of these shapes are similar to the yellow one?25431768AnswersHintsStart page

• Similar shapes are all shown in yellow were you right?25431768Start page

• What makes a pair of shapes similar?Same anglesSides in the same proportionCan be rotated or reflectedOne is an enlargement of the otherScale factor gives degree of enlargement:Scale factor 2 size is doubledScale factor 0.5 size is halvedScale factor 1 size doesnt change congruent tooClick the green box if you want to go back to the similar shapes question page.Question pageStart page

• Using similarity9cm12cm6cmaSince shapes are similar, their sides are in the same proportionMultiply both sides by 12=> 12 x 6 = a 9=> a = 12 x 2 = 4 x 2 3 1Start page=> 6 = a 9 12=> a = 8cm

• Which of these shapes are similar to the yellow one?(They arent drawn to scale)432156AnswersStart page6969464.53121891248

• Similar shapes are shown in yellow were you right?Start page96

• Scale factor = new value old value. 8cm12cm5cm7.5cmNew value = Old valueNew value = Old valueStart page 12 = 3 or 1.5 8 2Can you see the relationship between the two scale factors? 8 = 212 3

• Using scale factor9cmaEnlarge with scale factor 3b15cma = 9 x 3 = 27cm SF = new/old = 9/27 = What will the scale factor be?b = 15 x = 15 3 = 5cm Start pageOR reciprocal of 3 =

• Similar shapes - summaryRatio a:b:c = ratio x:y:zSo: a = xa = x b = y b yc z c zTo see whether 2 shapes are similar, put each ratio in its simplest form and see if they match.Scale factor = new measurement old measurement- Scale factor more than 1 => shape gets bigger Scale factor less than 1 => shape gets smaller Congruent shapes are similar shapes with SF = 1Old measurement x SF = new measurementRemember: only side lengths change; angles stay the same!