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Randy has a cube with an edge of 21 cm. From one corner of this cube Randy cuts and removes a cube with an edge of 15 cm. Find the percentage change in surface area of the original cube.

Guest Feb 5, 2018
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 #1
avatar+11453 
+2

Original surface area    21 x 21 x 6 sides =2646 cm^2

 

New surface area    21 x 21 x 3 sides    +  15x15x3   +  (21 x 21 - (15x15) ) x 3

                                   1323                +          675            +     648

                                     2646 cm^2

No change in surface area

ElectricPavlov  Feb 5, 2018
edited by Guest  Feb 5, 2018
 #2
avatar+82944 
+2

Thanks, EP.....to see this more clearly.....note that  the cube that is removed had three exposed sides contributing to the original surface area of the original cube

 

But...note when the smaller cube is removed....the same surface areas remain on the  altered cube

 

 

cool cool cool

CPhill  Feb 5, 2018
edited by CPhill  Feb 5, 2018

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