To find out how much space Robert will have left after using the squares, we first need to calculate the area occupied by the 10 squares with sides of 7 inches.
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Calculate the area of one square: \[ s^2 = 7^2 = 49 \text{ square inches} \]
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Calculate the total area occupied by 10 squares: \[ 10s^2 = 10 \times 49 = 490 \text{ square inches} \]
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Now, subtract the total area of the squares from the area of the poster board: \[ 720 - 10s^2 = 720 - 490 = 230 \text{ square inches} \]
Thus, the space Robert will have left for his presentation is 230 square inches.