Round Decimals

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Answer Key & Explanations

Round Decimals · Grade 4 · Worksheet 1

1. Aroha is looking at a number line on her math worksheet. The number line shows a point labeled at 12.73. She needs to round this decimal to the nearest tenth. What is 12.73 rounded to the nearest tenth? Answer: 12.7 Solution: Identify the digit in the tenths place. In 12.73, the tenths digit is 7 (since the number is 12 and 73 hundredths, so 7 tenths). Look at the digit in the hundredths place.
   Full step-by-step solution

   Step 1: Identify the digit in the tenths place. In 12.73, the tenths digit is 7 (since the number is 12 and 73 hundredths, so 7 tenths). Step 2: Look at the digit in the hundredths place. That digit is 3. Step 3: Since 3 is less than 5, we round down. This means the tenths digit stays as 7. Step 4: All digits after the tenths place become zero, so we write 12.7. The answer is 12.7.

2. A rectangular garden has a length of 12.75 meters and a width of 8.35 meters. What is the area of the garden, rounded to the nearest tenth of a square meter? Answer: 106.5 Solution: We are given the length and width of a rectangular garden. Length = 12.75 m Width = 8.35 m We need to find the area and round it to the nearest tenth of a square meter.
   Full step-by-step solution

   Step 1: Understand the problem We are given the length and width of a rectangular garden. Length = 12.75 m Width = 8.35 m We need to find the area and round it to the nearest tenth of a square meter. Step 2: Recall the formula for area of a rectangle Area = length × width Step 3: Multiply the given numbers 12.75 × 8.35 First, break it down: 12.75 × 8.35 = 12.75 × (8 + 0.35) = (12.75 × 8) + (12.75 × 0.35) Step 4: Calculate 12.75 × 8 12.75 × 8 = 102.00 Step 5: Calculate 12.75 × 0.35 12.75 × 0.35 = 12.75 × (35/100) But let's multiply directly: 12.75 × 0.35 First, 12.75 × 0.3 = 3.825 Then, 12.75 × 0.05 = 0.6375 Add: 3.825 + 0.6375 = 4.4625 Step 6: Add the two parts 102.00 + 4.4625 = 106.4625 Step 7: Round to the nearest tenth 106.4625 Look at the hundredths digit: 6 (which is 5 or greater) So we round the tenths digit (4) up by 1 → 106.5 Step 8: Final answer Area = 106.5 square meters

3. Round 9.47 to the nearest whole number = ? Answer: 9 Solution: Identify the digit in the ones (whole number) place: 9.47 has 9 in the ones place. Look at the digit in the tenths place: 9.47 has 4 in the tenths place. Since 4 is less than 5, we do not round up.
   Full step-by-step solution

   Step 1: Identify the digit in the ones (whole number) place: 9.47 has 9 in the ones place. Step 2: Look at the digit in the tenths place: 9.47 has 4 in the tenths place. Step 3: Since 4 is less than 5, we do not round up. The ones digit stays 9. Step 4: The number 9.47 rounded to the nearest whole number is 9. The answer is 9.

4. Liam is drawing a large square on graph paper. Each side of the square measures 7.3 centimeters. What is the perimeter of the square? Round your answer to the nearest whole number. Answer: 29 Solution: A square has 4 equal sides. To find the perimeter, multiply the side length by 4. Side length = 7.3 cm.
   Full step-by-step solution

   Step 1: A square has 4 equal sides. To find the perimeter, multiply the side length by 4. Step 2: Side length = 7.3 cm. Multiply: 7.3 × 4 = 29.2 cm. Step 3: Now round 29.2 to the nearest whole number. Look at the tenths digit: 2. Since 2 is less than 5, we round down, so 29.2 rounds to 29. Step 4: The perimeter rounded to the nearest whole number is 29 cm. The answer is 29.

5. Matiu is drawing a large rectangular field on a grid where each square unit represents 1 square meter. The field measures 47.8 meters long and 32.3 meters wide. What is the area of the field? Round your answer to the nearest whole number. Answer: 1544 Solution: Recall that area of a rectangle = length × width. Multiply 47.8 × 32.3. First multiply 47.8 × 32 = 1529.6.
   Full step-by-step solution

   Step 1: Recall that area of a rectangle = length × width. Step 2: Multiply 47.8 × 32.3. Step 3: First multiply 47.8 × 32 = 1529.6. Step 4: Then multiply 47.8 × 0.3 = 14.34. Step 5: Add the results: 1529.6 + 14.34 = 1543.94. Step 6: Round 1543.94 to the nearest whole number. The digit in the tenths place is 9, which is 5 or greater, so we round up: 1543.94 rounds to 1544. Step 7: Include the units: 1544 square meters. The answer is 1544.