Add/Subtract Decimals

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Answer Key & Explanations

Add/Subtract Decimals · Grade 4 · Worksheet 1

1. A rectangular swimming pool is drawn with a length of 15.25 meters and a width of 8.5 meters. A decorative tile border is placed around the entire edge of the pool. What is the total length of the tile border in meters? Answer: 47.5 Solution: Recall the formula for the perimeter of a rectangle. Perimeter = 2 × (length + width) Substitute the given values into the formula. Perimeter = 2 × (15.25 + 8.5) Add the length and width.
   Full step-by-step solution

   Step 1: Recall the formula for the perimeter of a rectangle. Perimeter = 2 × (length + width) Step 2: Substitute the given values into the formula. Perimeter = 2 × (15.25 + 8.5) Step 3: Add the length and width. 15.25 + 8.5 = 23.75 Step 4: Multiply by 2. 2 × 23.75 = 47.5 Step 5: State the final answer. The total length of the tile border is 47.5 meters.

2. 15.75 - 8.49 = ? Answer: 7.26 Solution: Write the numbers vertically, aligning the decimal points: 15.75 - 8.49 Start subtracting from the rightmost column (hundredths place): 5 - 9, we need to regroup from the tenths place Regroup from tenths place: 7 becomes 6, and 5 becomes 15 15 - 9 = 6 (hundredths place) Move to tenths place: 6…
   Full step-by-step solution

   Step 1: Write the numbers vertically, aligning the decimal points: 15.75 - 8.49 Step 2: Start subtracting from the rightmost column (hundredths place): 5 - 9, we need to regroup from the tenths place Step 3: Regroup from tenths place: 7 becomes 6, and 5 becomes 15 15 - 9 = 6 (hundredths place) Step 4: Move to tenths place: 6 - 4 = 2 (tenths place) Step 5: Move to ones place: 5 - 8, we need to regroup from tens place Step 6: Regroup from tens place: 1 becomes 0, and 5 becomes 15 15 - 8 = 7 (ones place) Step 7: Tens place: 0 - 0 = 0 Step 8: Bring down the decimal point Step 9: Final answer: 7.26 The answer is 7.26.

3. Liam bought a new backpack for $24.75 and a set of colored pencils for $8.50. He gave the cashier $40.00. How much change should Liam receive? Answer: 6.75 Solution: Add the cost of the backpack and the colored pencils. Backpack: 24.75 Colored pencils: 8.50 Total cost = 24.75 + 8.50 24.75 + 8.50 = 33.25 So, the total amount Liam spent is $33.25.
   Full step-by-step solution

   First, we need to find the total cost of the items Liam bought. Step 1: Add the cost of the backpack and the colored pencils. Backpack: 24.75 Colored pencils: 8.50 Total cost = 24.75 + 8.50 Let's add them: 24.75 + 8.50 = 33.25 So, the total amount Liam spent is $33.25. Step 2: Subtract the total cost from the amount he gave the cashier to find the change. Amount given: 40.00 Total cost: 33.25 Change = 40.00 - 33.25 Let's subtract: 40.00 - 33.25 = 6.75 Therefore, Liam should receive $6.75 in change. Final Answer: 6.75

4. Nikau had 38 dollars. Then Nikau spent 2 dollars at the store. How much money does Nikau have left? Answer: 36 Solution: Start with 38 dollars. Subtract the amount spent: 38 - 2 = 36. Nikau has 36 dollars left.
   Full step-by-step solution

   Step 1: Start with 38 dollars. Step 2: Subtract the amount spent: 38 - 2 = 36. Nikau has 36 dollars left.

5. Emma is saving money for a new bicycle. She already has $125.75 in her piggy bank. For her birthday, her grandparents give her $50.25. How much money does Emma have now? Answer: 176.00 Solution: Write down the amounts Emma has. Starting amount: $125.75 Birthday money: $50.25 Add the two amounts together. 125.75 + 50.25 Add the hundredths place (cents).
   Full step-by-step solution

   Step 1: Write down the amounts Emma has. Starting amount: $125.75 Birthday money: $50.25 Step 2: Add the two amounts together. 125.75 + 50.25 ________ Step 3: Add the hundredths place (cents). 5 hundredths + 5 hundredths = 10 hundredths 10 hundredths = 1 tenth and 0 hundredths Write 0 in the hundredths place and carry 1 to the tenths place. Step 4: Add the tenths place. 7 tenths + 2 tenths = 9 tenths Plus the carried 1 tenth = 10 tenths 10 tenths = 1 whole and 0 tenths Write 0 in the tenths place and carry 1 to the ones place. Step 5: Add the ones place. 5 ones + 0 ones = 5 ones Plus the carried 1 one = 6 ones Write 6 in the ones place. Step 6: Add the tens place. 2 tens + 5 tens = 7 tens Write 7 in the tens place. Step 7: Add the hundreds place. 1 hundred + 0 hundreds = 1 hundred Write 1 in the hundreds place. Step 8: Combine all the results. The total is 176.00 Emma now has $176.00.

6. Emma is training for a marathon. On Monday, she ran 3.25 kilometers. On Tuesday, she ran 4.75 kilometers. How many total kilometers did Emma run on these two days? Answer: 8.00 Solution: Monday: 3.25 kilometers Tuesday: 4.75 kilometers 3 + 4 = 7 0.25 + 0.75 = 1.00 7 + 1.00 = 8.00 Emma ran 8.00 kilometers total during these two days.
   Full step-by-step solution

   Step 1: Write down the distances Emma ran each day Monday: 3.25 kilometers Tuesday: 4.75 kilometers Step 2: Add the whole number parts 3 + 4 = 7 Step 3: Add the decimal parts 0.25 + 0.75 = 1.00 Step 4: Combine the results 7 + 1.00 = 8.00 Emma ran 8.00 kilometers total during these two days.

7. Liam is measuring ribbon for a craft project. He needs 2.75 meters of blue ribbon and 1.25 meters of red ribbon. How many meters of ribbon does Liam need in total? Answer: 4.00 Solution: Identify the amounts of ribbon needed. Liam needs 2.75 meters of blue ribbon and 1.25 meters of red ribbon. Write the addition expression for the total.
   Full step-by-step solution

   Step 1: Identify the amounts of ribbon needed. Liam needs 2.75 meters of blue ribbon and 1.25 meters of red ribbon. Step 2: Write the addition expression for the total. Total = 2.75 + 1.25 Step 3: Add the numbers. First, add the hundredths place: 0.75 + 0.25 = 1.00 So, 2.75 + 1.25 = (2 + 1) + (0.75 + 0.25) = 3 + 1.00 = 4.00 Step 4: State the final answer. Liam needs 4.00 meters of ribbon in total.