Estimation

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Answer Key & Explanations

Estimation · Grade 3 · Worksheet 2

1. Isabella is helping her dad organize the family's books. She counts 637 books on the main shelf and 289 books in the storage bin. About how many books do they have in total? Round each number to the nearest hundred before estimating the sum. Answer: 900 Solution: Round 637 to the nearest hundred. The tens digit is 3, which is less than 5, so we round down. 637 rounds to 600.
   Full step-by-step solution

   Step 1: Round 637 to the nearest hundred. The tens digit is 3, which is less than 5, so we round down. 637 rounds to 600. Step 2: Round 289 to the nearest hundred. The tens digit is 8, which is 5 or more, so we round up. 289 rounds to 300. Step 3: Add the rounded numbers: 600 + 300 = 900. The estimated total number of books is about 900.

2. 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.

3. Noah is looking at a rectangular garden drawn on a grid. The garden measures 86 centimeters long and 51 centimeters wide. Estimate the perimeter of the garden by rounding each measurement to the nearest ten first. What is the estimated perimeter? Answer: 280 Solution: Round each measurement to the nearest ten. 86 has a ones digit of 6, which is 5 or more, so it rounds up to 90. 51 has a ones digit of 1, which is less than 5, so it rounds down to 50.
   Full step-by-step solution

   Step 1: Round each measurement to the nearest ten. 86 has a ones digit of 6, which is 5 or more, so it rounds up to 90. 51 has a ones digit of 1, which is less than 5, so it rounds down to 50. Step 2: The rounded length is 90 cm and the rounded width is 50 cm. Step 3: The formula for the perimeter of a rectangle is P = 2 x (length + width). Step 4: Add the rounded length and width: 90 + 50 = 140. Step 5: Multiply by 2: 2 x 140 = 280. The estimated perimeter is 280 centimeters.

4. A rectangular classroom floor is drawn with a length of 75 feet and a width of 42 feet. What is the perimeter of the classroom floor? Answer: 234 feet Solution: The formula for the perimeter of a rectangle is P = 2 × (length + width) Substitute the given values: P = 2 × (75 + 42) Add the length and width: 75 + 42 = 117 Multiply by 2: 2 × 117 = 234 Include the unit: 234 feet The perimeter of the classroom floor is 234 feet.
   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 × (75 + 42) Step 3: Add the length and width: 75 + 42 = 117 Step 4: Multiply by 2: 2 × 117 = 234 Step 5: Include the unit: 234 feet The perimeter of the classroom floor is 234 feet.

5. Aroha is collecting donations for her school's sports day. She received 437 cans of juice from one store and 268 cans from another store. About how many cans of juice did Aroha collect in total? Round each number to the nearest hundred before estimating the sum. Answer: 700 Solution: Round 437 to the nearest hundred. The tens digit is 3, which is less than 5, so we round down. 437 rounds to 400.
   Full step-by-step solution

   Step 1: Round 437 to the nearest hundred. The tens digit is 3, which is less than 5, so we round down. 437 rounds to 400. Step 2: Round 268 to the nearest hundred. The tens digit is 6, which is 5 or more, so we round up. 268 rounds to 300. Step 3: Add the rounded numbers: 400 + 300 = 700. The estimated total number of cans of juice Aroha collected is about 700.