Answer:
(d) 30 units²
Explanation:
The area of the rectangle is the product of the length and width. It is equal to the number of unit squares that fill the rectangle.
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By counting grid squares or subtracting coordinates, we can see this rectangle is 3 units wide and 10 units high. Its area will be ...
A = WH
A = (3 units)(10 units) = 30 units²
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Additional comment
You can also count the three columns of 10 shaded squares, or the 10 rows of 3 shaded squares. Either way, you will count 30 square units covering the rectangle.