Solved Exercises on One-Step Word Problems with Measurement Units in Grade 3

Master measurement word problems: length, time, liquid volume, and weight through these 5 detailed exercises with step-by-step solutions.

Solution: Exercises 1 to 3
1 Length word problem
Exercise 1
Maria has a piece of string that is 150 cm long. She cuts off 75 cm. How long is the remaining piece of string?
Definition:

Length: Distance between two points, measured in centimeters (cm), meters (m), etc.

Problem-solving method:
  1. Read the problem carefully
  2. Identify what is known and what is asked
  3. Choose the operation (addition, subtraction, etc.)
  4. Solve the problem
  5. Check your answer
Original length
150 cm
Cut off
75 cm
Remaining
150 - 75 = 75 cm
Step 1: Identify what we know

Original string length: 150 cm

Amount cut off: 75 cm

Step 2: Identify what we need to find

How long is the remaining piece?

Step 3: Choose the operation

We need to subtract because we're removing part of the string

Step 4: Solve the problem

150 cm - 75 cm = 75 cm

Step 5: Check the answer

75 cm + 75 cm = 150 cm ✓

150 cm - 75 cm = 75 cm
Final answer:

The remaining piece of string is 75 cm long

Applied rules:

• Subtraction: When taking away, use subtraction

• Same units: Both measurements in centimeters

• Checking: Add back to verify the answer

2 Time word problem
Exercise 2
A movie starts at 2:30 PM and lasts for 90 minutes. What time does the movie end?
Definition:

Time: Duration or moment, measured in hours, minutes, seconds

Start time
2:30 PM
Duration
90 min = 1 hr 30 min
End time
2:30 + 1:30 = 4:00 PM
Step 1: Convert the duration to hours and minutes

90 minutes = 60 minutes + 30 minutes = 1 hour 30 minutes

Step 2: Add the duration to the start time

2:30 PM + 1 hour 30 minutes

Step 3: Calculate the end time

2:30 + 1:00 = 3:30, then 3:30 + 0:30 = 4:00 PM

Step 4: State the final answer

The movie ends at 4:00 PM

2:30 PM + 90 min = 4:00 PM
Final answer:

The movie ends at 4:00 PM

Applied rules:

• Time conversion: 60 minutes = 1 hour

• Addition: Add duration to start time

• Carrying: When minutes exceed 60, convert to hours

3 Liquid volume word problem
Exercise 3
A juice container holds 2 liters of juice. If 750 mL of juice is poured out, how much juice is left in milliliters?
Definition:

Liquid volume: Amount of liquid, measured in liters (L) or milliliters (mL)

Original amount
2 L = 2,000 mL
Poured out
750 mL
Remaining
2,000 - 750 = 1,250 mL
Step 1: Convert liters to milliliters

2 L × 1,000 = 2,000 mL

Step 2: Identify the operation needed

We need to subtract because juice is being poured out

Step 3: Perform the subtraction

2,000 mL - 750 mL = 1,250 mL

Step 4: State the final answer

There are 1,250 mL of juice left

2 L - 750 mL = 1,250 mL
Final answer:

There are 1,250 mL of juice left in the container

Applied rules:

• Unit conversion: 1 L = 1,000 mL

• Subtraction: When taking away, use subtraction

• Same units: Convert to same units before calculating

Key Concepts: Measurement Word Problems
1 km = 1,000 m
Length Conversion
1 L = 1,000 mL
Volume Conversion
1 kg = 1,000 g
Weight Conversion
Problem-Solving Steps
5 Steps
Read → Identify → Choose → Solve → Check
Addition Key Words
Total, More, Plus
Combine or increase
Subtraction Key Words
Less, Take Away, Left
Remove or decrease
Key definitions:

One-step word problem: A problem that requires only one mathematical operation to solve

Length: Distance between two points (cm, m, km)

Time: Duration or moment (seconds, minutes, hours)

Liquid volume: Amount of liquid (mL, L)

Weight/Mass: Amount of matter (g, kg)

Complete methodology:
  1. Read carefully: Understand the situation described
  2. Identify information: Find what is given and what is asked
  3. Look for clues: Find words that indicate the operation needed
  4. Set up equation: Write the mathematical sentence
  5. Solve: Perform the calculation
  6. Check: Make sure the answer makes sense
Tip 1: Circle important numbers and underline the question in the problem.
Tip 2: Draw a picture or diagram to visualize the problem.
Tip 3: Always check that your answer uses the correct units.
Tip 4: If units are different, convert to the same unit before solving.
Key words: "how many more" = addition, "left over" = subtraction, "total" = addition, "less than" = subtraction.
Common conversions: 1 m = 100 cm, 1 km = 1,000 m, 1 L = 1,000 mL, 1 kg = 1,000 g.
Essential rules to remember:

• Read the entire problem before starting

• Identify what is being asked

• Look for clue words indicating operations

• Convert units to match before calculating

• Always include the correct unit in your answer

Solution: Exercises 4 to 5
4 Weight word problem
Exercise 4
A bag of apples weighs 3 kg. If 1,200 g of apples are eaten, how many grams of apples are left?
Definition:

Weight: The heaviness of an object, measured in grams (g) or kilograms (kg)

Original weight
3 kg = 3,000 g
Eaten amount
1,200 g
Remaining
3,000 - 1,200 = 1,800 g
Step 1: Convert kilograms to grams

3 kg × 1,000 = 3,000 g

Step 2: Identify the operation needed

We need to subtract because apples are being eaten (taken away)

Step 3: Perform the subtraction

3,000 g - 1,200 g = 1,800 g

Step 4: State the final answer

There are 1,800 g of apples left

3 kg - 1,200 g = 1,800 g
Final answer:

There are 1,800 grams of apples left in the bag

Applied rules:

• Unit conversion: 1 kg = 1,000 g

• Subtraction: When taking away, use subtraction

• Same units: Convert to same units before calculating

5 Mixed measurement word problem
Exercise 5
Tom's rope is 2 meters long. He needs 300 cm more rope to reach his friend's house. What is the total length of rope he needs in centimeters?
Definition:

Mixed units: Problems containing different measurement units that need to be converted

Current length
2 m = 200 cm
Additional needed
300 cm
Total needed
200 + 300 = 500 cm
Step 1: Convert meters to centimeters

2 m × 100 = 200 cm

Step 2: Identify the operation needed

We need to add because Tom needs more rope in addition to what he already has

Step 3: Perform the addition

200 cm + 300 cm = 500 cm

Step 4: State the final answer

Tom needs a total of 500 cm of rope

2 m + 300 cm = 500 cm
Final answer:

Tom needs a total of 500 centimeters of rope

Applied rules:

• Unit conversion: 1 m = 100 cm

• Addition: When combining amounts, use addition

• Same units: Convert to same units before calculating

Complete Guide: Solving Measurement Word Problems
1 km = 1,000 m
Length Conversion
Key definitions:

Word problem: A mathematical problem expressed in ordinary language that requires mathematical operations to solve

One-step problem: A problem that can be solved with a single mathematical operation (addition, subtraction, multiplication, or division)

Clue words: Words in the problem that suggest which operation to use

Measurement units: Standard quantities used to express physical properties (length, time, volume, weight)

Complete problem-solving methodology:
  1. Read the problem carefully: Understand what is happening in the story
  2. Identify known information: Circle numbers and identify their units
  3. Identify what is asked: Underline or highlight the question
  4. Look for clue words: Find words that indicate the operation needed
  5. Draw a picture (optional): Visualize the problem if helpful
  6. Set up the equation: Write the mathematical sentence
  7. Convert units if necessary: Make sure all measurements use the same unit
  8. Solve the equation: Perform the calculation
  9. Write the answer: Include the correct unit
  10. Check your answer: Does it make sense in the context of the problem?
Tip 1: Make a table to organize information when dealing with multiple measurements.
Tip 2: Use estimation to check if your answer is reasonable.
Tip 3: Practice with real objects to build intuition about measurement units.
Tip 4: Remember: when adding or subtracting measurements, units must be the same.
Operation clue words: Addition (+): total, sum, altogether, combined, more. Subtraction (-): difference, less, fewer, left, remaining.
Common mistakes: Forgetting to convert units, misreading the question, using wrong operation based on clue words.
Essential rules to know:

• Unit consistency: Always convert measurements to the same unit before calculating

• Operation identification: Use clue words to determine the correct operation

• Answer format: Always include the correct measurement unit in your answer

• Reasonableness: Check if your answer makes sense in the real world

• Problem comprehension: Read the entire problem before beginning calculations

Questions & Answers

Question: I always get confused about when to add and when to subtract in word problems. How do I know which one to use?

Answer: Look for clue words that tell you what to do:

  • Addition words: "total," "altogether," "combined," "more," "in all," "sum," "added to"
  • Subtraction words: "left," "remaining," "less," "take away," "difference," "how many more," "decreased by"

Also think about the situation:

  • Adding means combining or getting more → use addition
  • Taking away or finding what's left → use subtraction

Example: "Sarah had 5 apples and got 3 more" → addition (5 + 3)

Example: "Sarah had 5 apples and ate 3" → subtraction (5 - 3)

Question: When do I need to convert units in a word problem? How do I know?

Answer: You need to convert units when:

  • The problem gives measurements in different units (like meters and centimeters)
  • You need to perform operations (add, subtract) with different units
  • The answer is asked in a different unit than what's given

Always look at the units:

  • Before adding or subtracting, make sure both numbers have the same unit
  • If they don't, convert one to match the other
  • Your final answer should be in the unit requested by the problem

Example: If you have 2 meters and 30 centimeters, convert both to centimeters (200 cm + 30 cm = 230 cm) before adding.

Question: What should I do if I'm not sure my answer is correct?

Answer: Here are several ways to check your answer:

  • Estimate: Round numbers and see if your answer is close to your estimate
  • Reverse operation: If you added, subtract to check. If you subtracted, add to check
  • Reasonableness: Does your answer make sense in the real world?
  • Re-read: Go back and make sure you answered the question that was asked

Example: If you calculated that a person weighs 500 kg, that's probably wrong because adults typically weigh 50-100 kg. Your answer might be too big!

Always ask yourself: "Does this answer seem reasonable?"