Round Decimals

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Answer Key & Explanations

Round Decimals · Grade 4 · Worksheet 3

1. Emma is baking cookies for her class party. She needs 2.5 cups of flour for the chocolate chip cookies and 1.75 cups of flour for the sugar cookies. How many total cups of flour does Emma need for all the cookies? Answer: 4.25 Solution: Identify the amounts of flour needed: 2.5 cups for chocolate chip cookies and 1.75 cups for sugar cookies. Add the two amounts together: 2.5 + 1.75 2.50 + 1.75 4.25 The total amount of flour needed is 4.25 cups.
   Full step-by-step solution

   Step 1: Identify the amounts of flour needed: 2.5 cups for chocolate chip cookies and 1.75 cups for sugar cookies. Step 2: Add the two amounts together: 2.5 + 1.75 Step 3: Line up the decimal points and add: 2.50 + 1.75 ------- 4.25 Step 4: The total amount of flour needed is 4.25 cups.

2. Sophia is drawing a large number line on the ground. She marks the point for 4.61. Then she draws a point that is exactly halfway between 4.61 and the next whole number. What is the value of that point? Round your answer to the nearest tenth. Answer: 4.8 Solution: Identify the next whole number after 4.61. The next whole number is 5. Step 2: Find the number halfway between 4.61 and 5.
   Full step-by-step solution

   Step 1: Identify the next whole number after 4.61. The next whole number is 5. Step 2: Find the number halfway between 4.61 and 5. The halfway point is (4.61 + 5) / 2 = 9.61 / 2 = 4.805. Step 3: Round 4.805 to the nearest tenth. The tenths digit is 8. Look at the hundredths digit: it is 0. Since 0 is less than 5, we do not round up. So 4.805 rounded to the nearest tenth is 4.8. The answer is 4.8.

3. Emma is baking cookies for a school bake sale. Her recipe calls for 1.25 cups of chocolate chips and 0.75 cups of walnuts. How many total cups of these ingredients does Emma need for her cookies? Answer: 2.00 Solution: Identify the amounts to add: 1.25 cups of chocolate chips and 0.75 cups of walnuts Set up the addition: 1.25 + 0.75 Add the hundredths place: 5 + 5 = 10, write 0 and carry over 1 to the tenths place Add the tenths place: 2 + 7 + 1 (carried over) = 10, write 0 and carry over 1 to the ones place…
   Full step-by-step solution

   Step 1: Identify the amounts to add: 1.25 cups of chocolate chips and 0.75 cups of walnuts Step 2: Set up the addition: 1.25 + 0.75 Step 3: Add the hundredths place: 5 + 5 = 10, write 0 and carry over 1 to the tenths place Step 4: Add the tenths place: 2 + 7 + 1 (carried over) = 10, write 0 and carry over 1 to the ones place Step 5: Add the ones place: 1 + 0 + 1 (carried over) = 2 Step 6: Combine all parts: 2.00 The answer is 2.00 cups.

4. 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 her cookies? Answer: 2.00 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, write 0 in hundredths place, carry 1 to tenths place Add the tenths place: 2 + 7 + 1 (carried) = 10, write 0 in tenths…
   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 hundredths place, carry 1 to tenths place Step 4: Add the tenths place: 2 + 7 + 1 (carried) = 10, write 0 in tenths place, carry 1 to ones place Step 5: Add the ones place: 1 + 0 + 1 (carried) = 2 Step 6: The total is 2.00 cups Emma needs 2.00 total cups of chips for her cookies.

5. 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.

6. Noah is drawing a large circle on a grid where each small square represents 1 square centimeter. The circle has a radius of 7.4 centimeters. What is the area of the circle? Round your answer to the nearest whole number. (Use π = 3.14) Answer: 172 Solution: Recall the formula for the area of a circle: Area = π × radius × radius, or A = πr². The radius is 7.4 cm. First, find the radius squared: 7.4 × 7.4.
   Full step-by-step solution

   Step 1: Recall the formula for the area of a circle: Area = π × radius × radius, or A = πr². Step 2: The radius is 7.4 cm. First, find the radius squared: 7.4 × 7.4. Step 3: Multiply 7.4 × 7.4. Multiply 74 × 74 = 5476. Since there are two decimal places total (one in each factor), the product has two decimal places: 54.76. Step 4: Now multiply by π (3.14): 3.14 × 54.76. Step 5: Multiply 314 × 5476 = 1,719,464. There are four decimal places total (two in 3.14 and two in 54.76), so the product is 171.9464. Step 6: Round 171.9464 to the nearest whole number. Look at the tenths digit: 9. Since 9 is 5 or greater, we round the ones digit up. 171 rounds up to 172. Step 7: The area of the circle is approximately 172 square centimeters. The answer is 172.

7. Hana is measuring the height of her sunflower plant each week. Last week, the plant was 14.6 centimeters tall. This week, it has grown to 22.3 centimeters. What is the height of the sunflower plant rounded to the nearest whole centimeter? Answer: 22 Solution: Look at the number 22.3. The digit in the tenths place is 3. Step 2: When rounding to the nearest whole number, if the tenths digit is 5 or greater, we round up.
   Full step-by-step solution

   Step 1: Look at the number 22.3. The digit in the tenths place is 3. Step 2: When rounding to the nearest whole number, if the tenths digit is 5 or greater, we round up. If it is less than 5, we keep the whole number the same. Step 3: Since 3 is less than 5, we do not round up. Step 4: The whole number stays as 22. The answer is 22.