Estimation

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Answer Key & Explanations

Estimation · Grade 3 · Worksheet 2

1. Estimate: 589 - 312 (round to nearest 100) Answer: 300 Solution: Round 589 to the nearest 100. The tens digit is 8, which is 5 or more, so round up to 600. Round 312 to the nearest 100.
   Full step-by-step solution

   Step 1: Round 589 to the nearest 100. The tens digit is 8, which is 5 or more, so round up to 600. Step 2: Round 312 to the nearest 100. The tens digit is 1, which is less than 5, so round down to 300. Step 3: Subtract the rounded numbers: 600 - 300 = 300. The estimated difference is 300.

2. A rectangular soccer field is drawn with a length of 120 meters and a width of 80 meters. What is the perimeter of the soccer field? Answer: 400 Solution: The formula for the perimeter of a rectangle is P = 2 × (length + width). Substitute the given values: P = 2 × (120 + 80). First, add the length and width: 120 + 80 = 200.
   Full step-by-step solution

   Step 1: The formula for the perimeter of a rectangle is P = 2 × (length + width). Step 2: Substitute the given values: P = 2 × (120 + 80). Step 3: First, add the length and width: 120 + 80 = 200. Step 4: Then, multiply by 2: 2 × 200 = 400. The perimeter of the soccer field is 400 meters.

3. Estimate: 673 - 298 (round to nearest 100) Answer: 400 Solution: Round 673 to the nearest hundred. 673 is closer to 700 than to 600, so it rounds to 700. Round 298 to the nearest hundred.
   Full step-by-step solution

   Step 1: Round 673 to the nearest hundred. 673 is closer to 700 than to 600, so it rounds to 700. Step 2: Round 298 to the nearest hundred. 298 is closer to 300 than to 200, so it rounds to 300. Step 3: Subtract the rounded numbers: 700 - 300 = 400. The estimated difference is 400.

4. A rectangular playground is drawn on a grid. The playground has a length of 120 meters and a width of 85 meters. What is the total area of the playground in square meters? Answer: 10200 Solution: The formula for the area of a rectangle is length multiplied by width. The length is 120 meters and the width is 85 meters. Multiply 120 by 85.
   Full step-by-step solution

   Step 1: The formula for the area of a rectangle is length multiplied by width. Step 2: The length is 120 meters and the width is 85 meters. Step 3: Multiply 120 by 85. Step 4: First, multiply 120 by 80: 120 × 80 = 9600. Step 5: Then, multiply 120 by 5: 120 × 5 = 600. Step 6: Add the two results: 9600 + 600 = 10200. The total area is 10200 square meters.

5. Ava is collecting stickers for her scrapbook. She has 561 stickers from her first set and 286 stickers from her second set. About how many stickers does Ava have in total? Round each number to the nearest hundred before estimating the sum. Answer: 900 Solution: Round 561 to the nearest hundred. The tens digit is 6, which is 5 or more, so we round up. 561 rounds up to 600.
   Full step-by-step solution

   Step 1: Round 561 to the nearest hundred. The tens digit is 6, which is 5 or more, so we round up. 561 rounds up to 600. Step 2: Round 286 to the nearest hundred. The tens digit is 8, which is 5 or more, so we round up. 286 rounds up to 300. Step 3: Add the rounded numbers: 600 + 300 = 900. The estimated total number of stickers is about 900.