Estimating percents

 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.

$\large~\rightarrow$

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?) [show answer]   The square is about 70% shaded.

 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?) [show answer]   Can you see that the square is about 45% shaded? How close was your estimate?

 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?) [show answer]   Can you see that the square is about 25% shaded? How close was your estimate? Since this figure involved curved shapes, it was the hardest one to estimate. Don't worry if your estimate was way off!

Self-Check

Question 1

For this figure, what percent is shaded?

Which estimate is the best estimate: 78%, 88%, or 98%

Question 2

For this figure, what percent is shaded?

Which estimate is the best estimate: 40%, 50%, or 60%