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Growing Rectangles

Age 11 to 14
Challenge Level Yellow star
Secondary curriculum
  • Problem
  • Getting Started
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Growing Rectangles printable sheet


Imagine a rectangle with an area of $20$cm$^2$
What could its length and width be? List at least five different combinations.



If you enlarge each of your rectangles by a scale factor of 2, what would their new dimensions be?

What would their areas be?

What do you notice?


What happens when you enlarge rectangles with different areas by a scale factor of 2?



What if you enlarge them by a scale factor of 3? Or 4? Or 5 ...? Or $k$?

What if $k$ is a fraction?

Explain and justify any conclusions you come to.

Do your conclusions apply to plane shapes other than rectangles?
Enlarged shapes

 

 

 


Now explore what happens to the surface area and volume of different cuboids when they are enlarged by different scale factors.

 

 

 

Small and enlarged cuboid
 
Explain and justify your conclusions.

Do your conclusions apply to solids other than cuboids?






This problem is based on an idea suggested by Tabitha Gould.

 

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Explore the effect of combining enlargements.

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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