Reductions, Enlargements and the Scale Factor Now if the red square is the original drawing, what is the blue square called? What is the yellow square.

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Presentation transcript:

Reductions, Enlargements and the Scale Factor Now if the red square is the original drawing, what is the blue square called? What is the yellow square called? How could we determine how many times bigger the blue square is? How could we determine how many times smaller the yellow square is? What do we call that?

Reductions, Enlargements and the Scale Factor The red square has side lengths of 3. The blue square has side lengths of 6. So the enlargement has a scale factor of: Side length of scale drawing Side length of original drawing which reduces to

Reductions, Enlargements and the Scale Factor The red square has side lengths of 3. The yellow square has side lengths of 1. So the reduction has a scale factor of: Side length of scale drawing Side length of original drawing

Reductions, Enlargements and the Scale Factor The red square has side lengths of 3. The blue square has side lengths of 4. The yellow square has side lengths of 2. What are the scale factors of each? Side length of scale drawing Side length of original drawing Remember a fraction or decimal is okay

Reductions, Enlargements and the Scale Factor The red square has side lengths of 3. The blue square has side lengths of 4. The red square has side lengths of 3. The yellow square has side lengths of 2. Side length of scale drawing Side length of original drawing Side length of scale drawing Side length of original drawing or

Reductions, Enlargements and the Scale Factor 4 3 A BC Triangle ABC needs to be enlarged by a scale factor of 3. What do we need to do first? What do we need to do second? 5

4 3 A BC What do you notice about the new drawing? What about its ‘name’? The new triangle is called ________ with side lengths: A’B’ = _______ B’C’ = _______ A’C’ = _______ 5

4 8 9 J KL Triangle JKL needs to be reduced by a scale factor of 0.5. What are the new side lengths of triangle J’K’L’?

4 8 9 J KL J’K’ = 4 x ________ K’L’ = 8 x ________ J’L’ = 9 x _________ So Triangle J’K’L’ now looks like this:

STOP This picture of a stop sign is a reduction of a real stop sign…obviously. It is shown at a scale factor of 1:30. The side lengths of the scale drawing are 25mm. What is the original side length in cm of an actual stop sign?

STOP What is the original side length in cm of an actual stop sign? Multiply the side length by the ____________________. 25mm x _____ = 750mm Now convert 750mm to cm. 750mm x 1cm = 75cm 10 mm

STOP What is the original side length in cm of an actual stop sign? 750mm x 1cm = ________cm 10 mm So the original side length of the original stop sign was _________cm.