standard_description: Solve multi-step real-life and mathematical problems posed with positive and negative rational numbers in any form (whole numbers, fractions, and decimals), using tools strategically. Apply properties of operations to calculate with numbers in any form; convert between forms as appropriate; and assess the reasonableness of answers using mental computation and estimation strategies. For example: If a woman making $25 an hour gets a 10% raise, she will make an additional 1/10 of her salary an hour, or $2.50, for a new salary of $27.50. If you want to place a towel bar 9 3/4 inches long in the center of a door that is 27 1/2 inches wide, you will need to place the bar about 9 inches from each edge; this estimate can be used as a check on the exact computation.
problem_activity: Problem 1
Quiana measures the width of her doorway entrance using a measuring tape. She measures the width as 33 inches. She later finds a better tape measure that measures to the nearest half of an inch. After re-measuring, she determines that the actual measure of the doorway is 32 ½ inches.
a.   What is the amount of error from using the first measuring tape?
b.   What is the error as a percentage of the actual width?
Problem 2
Paul and Kimberly both estimate the weight of their dogs before bringing them to the vet. The table below shows each of their estimates along with the actual weights of the dogs from the vet’s office.
|                | **           Estimate (lbs.)          ** | **           Actual (lbs.)          ** |
|----------------|------------------------------------------|----------------------------------------|
|   Paul's dog   |                    10                    |                  11.5                  |
| Kimberly's dog |                    84                    |                  82.5                  |
Paul notices that both his and Kimberly’s estimates were only 1.5 pounds off from the actual weights. Paul says that means his estimate was as good as Kimberly’s estimate.
Do you agree with Paul? Find the percent error for each person’s guess of their dog’s weight, and use it in your answer.
Problem 3
In science class, Justine measured a rock sample and found it to be 15 grams. Her teacher told her that the scale is off and the actual weight is 0.3 grams more than her measurement.
What is the percent error? Give your answer to the nearest percent.


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