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how many 7" high x 16" long bricks will fit in a 72" wide x 120" high rectangle?
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I can put 10 times 7" along the 72" side (10 bricks)
and 7 times 16" along the 120" side ( 7 bricks)
(the simplest and the most obvious placement).
In this way I will put 10*7 = 70 bricks.
The entire area of the original rectangle is 72*120 = 8640 sq. in.
The covered are will be 70*112 = 7840 sq. in.
The difference (the uncovered area) will be 800 sq. in.
The area of a single brick is 7*16 = 112 sq. in.
The uncovered area is equivalent to 7+ bricks.
And what?