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!