Solved Exercises on Liters and Milliliters Word Problems in Grade 3

Master liters and milliliters: conversion, addition, subtraction, and comparison of liquid volumes through these 5 detailed exercises with visual examples.

Solution: Exercises 1 to 3
1 Conversion problem
Exercise 1
Sarah has 3 liters of juice. How many milliliters of juice does she have?
Definition:

Liter (L): A unit of liquid volume. Milliliter (mL): A smaller unit of liquid volume.

Conversion rule: 1 liter = 1,000 milliliters

Conversion method:
  1. Identify the number of liters given
  2. Multiply by 1,000 to convert to milliliters
  3. Write the answer with the mL unit
Given
3 liters
Conversion
3 × 1,000
Result
3,000 mL
Step 1: Identify the conversion factor

We know that 1 liter = 1,000 milliliters

Step 2: Set up the multiplication

3 liters × 1,000 milliliters per liter

Step 3: Calculate the result

3 × 1,000 = 3,000

Step 4: Add the unit

3,000 milliliters (mL)

3 liters = 3,000 milliliters
Final answer:

Sarah has 3,000 milliliters of juice.

Applied rules:

• Conversion: Multiply liters by 1,000 to get milliliters

• Unit conversion: Keep track of units during calculations

• Place value: Adding 3 zeros when multiplying by 1,000

2 Addition problem
Exercise 2
Tom poured 1,500 mL of water into a bucket. Then he added 800 mL more. How much water is in the bucket now?
Definition:

Addition: Combining two or more amounts of liquid volume to find the total.

Amount 1
1,500 mL
Amount 2
800 mL
Total
2,300 mL
Step 1: Identify the amounts to add

First amount: 1,500 mL, Second amount: 800 mL

Step 2: Add the amounts together

1,500 + 800 = 2,300

Step 3: Write the answer with the unit

2,300 milliliters (mL)

1,500 mL + 800 mL = 2,300 mL
Final answer:

There are 2,300 milliliters of water in the bucket.

Applied rules:

• Addition: Combine amounts when liquids are mixed together

• Same units: Only add when both amounts use the same unit

• Carrying over: Handle place values correctly during addition

3 Comparison problem
Exercise 3
Which container holds more liquid: a 2-liter bottle or a 1,800-milliliter bottle?
Definition:

Comparison: Determining which of two quantities is greater by converting to the same unit.

Bottle 1
2 L
Bottle 2
1,800 mL
Compare
2,000 vs 1,800
Step 1: Convert to the same unit

Convert 2 liters to milliliters: 2 × 1,000 = 2,000 mL

Step 2: Compare the amounts

2,000 mL vs 1,800 mL

Step 3: Determine which is greater

2,000 > 1,800, so the 2-liter bottle holds more

2,000 mL > 1,800 mL
Final answer:

The 2-liter bottle holds more liquid than the 1,800-milliliter bottle.

Applied rules:

• Conversion: Always convert to the same unit before comparing

• Comparison: Use >, <, or = to compare amounts

• Place value: Compare digits from left to right

Rules and methods, laws,...
1 L = 1,000 mL
Conversion Rule
Conversion
L to mL: × 1,000
1 L = 1,000 mL
Reverse
mL to L: ÷ 1,000
1,000 mL = 1 L
Addition
A + B = Total
Combine liquid volumes
Key definitions:

Liter (L): Standard unit for measuring liquid volume, larger than milliliter

Milliliter (mL): Smaller unit for measuring liquid volume

Conversion: Changing from one unit to another while keeping the same quantity

Complete methodology:
  1. Read the problem: Identify what is being measured and asked
  2. Identify units: Check if all measurements use the same unit
  3. Convert if needed: Change all measurements to the same unit
  4. Perform operation: Add, subtract, or compare as needed
  5. Check answer: Make sure it makes sense in the context
Tip 1: Remember: 1 liter is the same as 1,000 milliliters.
Tip 2: To convert liters to milliliters, multiply by 1,000.
Tip 3: To convert milliliters to liters, divide by 1,000.
Tip 4: Always make sure all measurements use the same unit before adding or comparing.
Common errors: Forgetting to convert units, miscounting zeros, confusing liters and milliliters.
Memory trick: Think of "milli" as meaning small, so milliliters are smaller than liters.
Formulas to know by heart:

• 1 liter = 1,000 milliliters

• Liters to milliliters: multiply by 1,000

• Milliliters to liters: divide by 1,000

• Always convert to same unit before adding or comparing

Solution: Exercises 4 to 5
4 Subtraction problem
Exercise 4
A large jug contains 4 liters of milk. After drinking some milk, there are 1,500 mL left. How much milk was drunk?
Definition:

Subtraction: Finding the difference between two amounts to determine what was removed.

Original
4 L
Remaining
1,500 mL
Consumed
2,500 mL
Step 1: Convert to the same unit

Convert 4 liters to milliliters: 4 × 1,000 = 4,000 mL

Step 2: Subtract the remaining amount from original

4,000 mL - 1,500 mL = 2,500 mL

Step 3: Write the answer with the unit

2,500 milliliters (mL)

Step 4: Verify the calculation

1,500 mL + 2,500 mL = 4,000 mL = 4 L ✓

4,000 mL - 1,500 mL = 2,500 mL
Final answer:

2,500 milliliters of milk were drunk.

Applied rules:

• Subtraction: Original - Remaining = Amount consumed

• Unit conversion: Always convert to same unit before subtracting

• Verification: Check by adding the result back to the remaining amount

5 Multi-step problem
Exercise 5
A store has 3 bottles of juice: one with 2 L, one with 1,500 mL, and one with 750 mL. How many total milliliters of juice does the store have?
Definition:

Multi-step problem: Requires multiple operations to solve, often involving conversion and addition.

Bottle 1
2 L
Bottle 2
1,500 mL
Bottle 3
750 mL
Total
4,250 mL
Step 1: Convert all amounts to the same unit

Convert 2 liters to milliliters: 2 × 1,000 = 2,000 mL

Step 2: List all amounts in milliliters

Bottle 1: 2,000 mL, Bottle 2: 1,500 mL, Bottle 3: 750 mL

Step 3: Add all amounts together

2,000 + 1,500 + 750 = 4,250 mL

Step 4: Verify the calculation

2,000 + 1,500 = 3,500; 3,500 + 750 = 4,250 ✓

2,000 mL + 1,500 mL + 750 mL = 4,250 mL
Final answer:

The store has 4,250 milliliters of juice in total.

Applied rules:

• Multi-step: Break complex problems into simpler steps

• Conversion: Convert all measurements to the same unit before adding

• Order of operations: Perform conversions before addition

Liquid Volume Measurement Guide: Definitions, Rules, Methods
1 L = 1,000 mL
Conversion Formula
Key definitions:

Liquid Volume: The amount of space a liquid takes up, measured in liters (L) or milliliters (mL)

Liter (L): A standard unit of liquid volume, approximately equal to the volume of a cube 10 cm on each side

Milliliter (mL): A smaller unit of liquid volume, where 1,000 milliliters equals 1 liter

Conversion: Changing from one unit of measurement to another without changing the actual amount

Complete methodology:
  1. Read the problem carefully: Identify what is being measured and what is being asked
  2. Identify the units involved: Check if all measurements use the same unit (L or mL)
  3. Convert if necessary: Change all measurements to the same unit before performing operations
  4. Perform the required operation: Add, subtract, multiply, or compare as needed
  5. Express the answer in the correct unit: Always include the appropriate unit (L or mL)
  6. Verify the answer: Check if the answer makes sense in the context of the problem
Tip 1: Remember the relationship: 1 L = 1,000 mL. Think of "kilo" as 1,000.
Tip 2: To convert liters to milliliters, move the decimal point 3 places to the right.
Tip 3: To convert milliliters to liters, move the decimal point 3 places to the left.
Tip 4: Always check that your answer has the correct unit and makes sense in the real world.
Common errors: Mixing units without conversion, misplacing decimal points, confusing liters with milliliters.
Real-world applications: Cooking, medicine dosages, science experiments, fuel measurement.
Essential formulas and rules:

• 1 liter = 1,000 milliliters

• Liters to milliliters: multiply by 1,000 (move decimal 3 places right)

• Milliliters to liters: divide by 1,000 (move decimal 3 places left)

• Always convert to same unit before adding, subtracting, or comparing

• In word problems, identify key words: "total," "more than," "less than," "combined"

Visual Guide: Liquid Volume Comparisons
Liquid Volume Visualization
Understanding how different volumes relate:
1 L = 1,000 mL
1/2 L = 500 mL
1/4 L = 250 mL
100 mL = 0.1 L

Analysis: The chart shows how different liquid volumes compare in both liters and milliliters.

  • 1 L = 1,000 mL (standard reference)
  • 1/2 L = 500 mL (half a liter)
  • 1/4 L = 250 mL (quarter of a liter)
  • 100 mL = 0.1 L (one-tenth of a liter)

Questions & Answers

Question: I don't understand why we need to convert liters to milliliters. Why can't we just keep everything in liters?

Answer: Great question! We convert to the same unit because:

  • You can't add or compare different units directly, just like you can't add 5 meters and 3 centimeters without converting first
  • Sometimes problems give you measurements in different units (some in liters, some in milliliters)
  • It helps us understand the actual amount better - 2,000 mL is easier to visualize than 2 L when thinking about individual drops

Think of it like money: if someone had $5 and 300 cents, you'd convert to the same unit (cents) to add them: 500 cents + 300 cents = 800 cents.

Example: If you have 1 L and 500 mL, converting both to mL gives you 1,000 mL + 500 mL = 1,500 mL total.

Question: When I convert liters to milliliters, I sometimes forget how many zeros to add. How can I remember?

Answer: Here are memory tricks to remember the conversion:

  • Think of "milli" as meaning "thousandth" - so 1,000 milliliters make 1 liter
  • Count the letters: "milliliter" has more letters than "liter," so milliliters are the smaller unit
  • Remember the pattern: kilo (1,000), hecto (100), deka (10), base (1), deci (0.1), centi (0.01), milli (0.001)

To convert liters to milliliters: multiply by 1,000 (add 3 zeros)

Examples: 3 L = 3,000 mL; 0.5 L = 500 mL; 2.5 L = 2,500 mL

Tip: Draw a number line showing how 1,000 mL fills up to 1 L to visualize the relationship!

Question: How do I know when a word problem needs addition versus subtraction?

Answer: Look for key words and actions in the problem:

  • Addition: Words like "total," "altogether," "combined," "more," "added," "drank and then drank more"
  • Subtraction: Words like "left," "remaining," "how much less," "drank," "used," "after taking away"

Examples:

  • "Tom poured 500 mL, then added 300 mL more" → Addition (500 + 300)
  • "Sarah had 1 L, then drank 200 mL" → Subtraction (1,000 - 200)

Always ask yourself: "Am I combining amounts or finding what's left?" This helps determine whether to add or subtract.