Round Decimals

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Answer Key & Explanations

Round Decimals · Grade 4 · Worksheet 2

1. Noah draws a number line from 0 to 10. He marks a point at 7.36. What is 7.36 rounded to the nearest whole number? Answer: 7 Solution: We need to round 7.36 to the nearest whole number. Step 2: Look at the digit in the tenths place, which is 3 (since 7.36 = 7 and 36 hundredths).
   Full step-by-step solution

   Step 1: We need to round 7.36 to the nearest whole number. Step 2: Look at the digit in the tenths place, which is 3 (since 7.36 = 7 and 36 hundredths). Step 3: The rule for rounding to the nearest whole number: if the tenths digit is 5 or greater, round up; if it is 4 or less, round down. Step 4: Here, the tenths digit is 3, which is less than 5, so we round down. Step 5: Rounding down means the whole number stays 7. Step 6: Therefore, 7.36 rounded to the nearest whole number is 7. The answer is 7.

2. Emma is baking cookies for her class party. The recipe calls for 1.25 cups of chocolate chips and 0.75 cups of peanut butter chips. How many total cups of chips does Emma need for the recipe? Answer: 2 Solution: Identify the amounts to add: 1.25 cups of chocolate chips and 0.75 cups of peanut butter chips. Write the addition problem: 1.25 + 0.75 Add the hundredths place: 5 + 5 = 10.
   Full step-by-step solution

   Step 1: Identify the amounts to add: 1.25 cups of chocolate chips and 0.75 cups of peanut butter chips. Step 2: Write the addition problem: 1.25 + 0.75 Step 3: Add the hundredths place: 5 + 5 = 10. Write 0 in the hundredths place and carry over 1 to the tenths place. Step 4: Add the tenths place: 2 + 7 + 1 (carried over) = 10. Write 0 in the tenths place and carry over 1 to the ones place. Step 5: Add the ones place: 1 + 0 + 1 (carried over) = 2. Step 6: The total is 2.00 cups, which is 2 cups. Emma needs 2 total cups of chips.

3. Liam is measuring ribbon for a school project. He needs 3.75 meters of blue ribbon and 2.25 meters of red ribbon. If the ribbon is sold by the meter, how many total meters of ribbon should Liam buy to have enough for his project? Answer: 6 Solution: - Blue ribbon: 3.75 meters - Red ribbon: 2.25 meters Ribbon is sold by the meter, so we must buy whole meters. We need enough ribbon for his project, so we must round up if there are decimals.
   Full step-by-step solution

   Let's go step-by-step. --- **Step 1: Understand the problem** Liam needs: - Blue ribbon: 3.75 meters - Red ribbon: 2.25 meters Ribbon is sold by the meter, so we must buy whole meters. We need enough ribbon for his project, so we must round up if there are decimals. --- **Step 2: Add the total meters needed** 3.75 + 2.25 = 6.00 meters exactly. --- **Step 3: Check if we need to round up** Since 6.00 is exactly 6 meters, and ribbon is sold by the meter, buying 6 meters will give exactly what he needs. --- **Step 4: Conclusion** Liam should buy **6 meters** of ribbon in total. --- **Final Answer:** 6

4. Sophia is training for a 5-kilometer fun run. On Monday, she ran 3.7 kilometers. On Tuesday, she ran 4.2 kilometers. Sophia wants to know her total distance for both days rounded to the nearest whole kilometer. What is the total distance rounded to the nearest whole kilometer? Answer: 8 Solution: Add the distances: 3.7 + 4.2 = 7.9 kilometers. To round 7.9 to the nearest whole number, look at the tenths digit. The tenths digit is 9.
   Full step-by-step solution

   Step 1: Add the distances: 3.7 + 4.2 = 7.9 kilometers. Step 2: To round 7.9 to the nearest whole number, look at the tenths digit. The tenths digit is 9. Step 3: Since 9 is greater than or equal to 5, we round up the whole number from 7 to 8. Step 4: The rounded total distance is 8 kilometers. Answer: 8

5. Round 12.47 to the nearest tenth = ? Answer: 12.5 Solution: Identify the digit in the tenths place. In 12.47, the tenths digit is 4. Look at the digit immediately to the right (the hundredths place).
   Full step-by-step solution

   Step 1: Identify the digit in the tenths place. In 12.47, the tenths digit is 4. Step 2: Look at the digit immediately to the right (the hundredths place). In 12.47, the hundredths digit is 7. Step 3: Since the hundredths digit (7) is 5 or greater, we round the tenths digit (4) up by 1. This makes the tenths digit become 5. Step 4: All digits to the right of the tenths place become zero, so 12.47 becomes 12.50, which is written as 12.5. The answer is 12.5.

6. Round 5.67 to the nearest tenth = ? Answer: 5.7 Solution: Identify the digit in the tenths place: 5.6 (6 is in the tenths place) Look at the digit in the hundredths place: 5.67 (7 is in the hundredths place) Since 7 is 5 or greater, round the tenths digit up from 6 to 7 The rounded number is 5.7 The answer is 5.7.
   Full step-by-step solution

   Step 1: Identify the digit in the tenths place: 5.6 (6 is in the tenths place) Step 2: Look at the digit in the hundredths place: 5.67 (7 is in the hundredths place) Step 3: Since 7 is 5 or greater, round the tenths digit up from 6 to 7 Step 4: The rounded number is 5.7 The answer is 5.7.

7. Charlotte is drawing a large square on a grid. Each side of the square measures 9.8 centimeters. What is the perimeter of the square? Round your answer to the nearest whole number. Answer: 39 Solution: Recall that the perimeter of a square is the sum of all four sides. Since all sides are equal, perimeter = 4 × side length. Multiply: 4 × 9.8 = 39.2.
   Full step-by-step solution

   Step 1: Recall that the perimeter of a square is the sum of all four sides. Since all sides are equal, perimeter = 4 × side length. Step 2: Multiply: 4 × 9.8 = 39.2. Step 3: Now round 39.2 to the nearest whole number. Look at the tenths digit: it is 2, which is less than 5, so we round down. Step 4: 39.2 rounded to the nearest whole number is 39. The answer is 39.

8. Liam is measuring ribbon for a school project. He needs 3.75 meters of blue ribbon and 2.25 meters of red ribbon. If the ribbon is sold by the meter, what is the total length of ribbon Liam needs to buy? Answer: 6 Solution: Identify the lengths needed. Blue ribbon: 3.75 meters Red ribbon: 2.25 meters Add the two lengths together. 3.75 + 2.25 = ?
   Full step-by-step solution

   Let's go step-by-step. Step 1: Identify the lengths needed. Blue ribbon: 3.75 meters Red ribbon: 2.25 meters Step 2: Add the two lengths together. 3.75 + 2.25 = ? Step 3: Break it down for clarity. 3.75 = 3 + 0.75 2.25 = 2 + 0.25 Step 4: Add the whole numbers first. 3 + 2 = 5 Step 5: Add the decimal parts. 0.75 + 0.25 = 1.00 Step 6: Combine whole and decimal parts. 5 + 1.00 = 6.00 Step 7: Interpret the result. The total length needed is 6.00 meters. Since ribbon is sold by the meter, Liam must buy 6 meters. Final answer: 6

9. Round 3.47 to the nearest tenth. Answer: 3.5 Solution: Identify the digit in the tenths place. In 3.47, the digit in the tenths place is 4. Look at the digit to the right (the hundredths place).
   Full step-by-step solution

   Step 1: Identify the digit in the tenths place. In 3.47, the digit in the tenths place is 4. Step 2: Look at the digit to the right (the hundredths place). The hundredths digit is 7. Step 3: Since the hundredths digit (7) is 5 or greater, we round the tenths digit (4) up by 1. 4 becomes 5. Step 4: The digits after the tenths place become zero, so 3.47 rounded to the nearest tenth is 3.5.