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(a) How many squares are in the grid below, that do not include the center red square?

 

(b) How many rectangles are in the grid below, that do not include the center red square?

 

 May 4, 2020
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So the only squares that don't include red are 1*1, and 2*2. 

 

There are 25-1 such 1*1, and... 12 2*2s.

 

remember they overlap!

 

24+12 = 36.

 

 

RECTANGLES.

 

Remember, a square is a rectangle but a rectangle isn't a square.

 

Well we already have the 36 squares. Onwards!

 

There can be... 1*2, 1*3, 1*4, 1*5, 2*3, 2*4, 2*5. Again, these can overlap.

 

There *should* be 36 1*2.

 

Do the rest yourself and if you don't understand anything ask!

 

:)

 May 4, 2020

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