Percent is a ratio in which one of the two numbers being compared is always 100. Percent means "per hundred". 28% means "28 parts out of 100 hundred parts". 
To estimate a percent of something, you must imagine that thing being cut up into exactly 100 parts. For example, if you were to estimate the percent of the square that is covered by the shaded figure you would need to imagine the square being cut up into 100 pieces. Then you would need to count the number of pieces that are shaded to estimate the percent.
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If you were to count carefully, you would find that this figure covers about 29 square units. This means the blob covers about 29% of the square.
Example 1 Estimate the percent of this square that is shaded. (HINT: Imagine the square being cut into 100 unit squares. How many squares would be shaded?)

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Example 2 Estimate the percent of this square that is shaded. (HINT: Imagine the square being cut into 100 unit squares. How many would be shaded?)

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Example 3 Estimate the percent of this square that is shaded. (HINT: Imagine the square being cut into 100 unit squares. How many would be shaded?)

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Question 1 For this figure, what percent is shaded? Which estimate is the best estimate: 78%, 88%, or 98%

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Question 2 For this figure, what percent is shaded? Which estimate is the best estimate: 40%, 50%, or 60%

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Question 3 For this figure, what percent is shaded? Which estimate is the best estimate: 25%, 35%, or 12%

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