Jugs and Mugs Class 4 NCERT Chapter 7 Guide

What is Capacity? Understanding Litres and Millilitres

Capacity is the amount of liquid a container can hold. For example, a large bucket has a bigger capacity than a tiny teacup because it can hold much more water. To measure capacity accurately, we use standard mathematical units instead of just guessing with words like 'big' or 'small'.

The two most common standard units of capacity are:

1. Litre (L): We use Litres to measure larger quantities of liquids. For example, a bottle of cold drink, a bucket of water, or fuel in a car tank are measured in Litres.
2. Millilitre (mL): We use Millilitres to measure smaller quantities of liquids. Examples include a spoonful of cough syrup, a small perfume bottle, or a cup of tea.

The Golden Rule of Capacity:
$1 \text{ Litre (L)} = 1000 \text{ Millilitres (mL)}$

This simple formula means that if you have a 1-litre jug, you can fill it completely using exactly ten small mugs of 100 mL each, or four medium mugs of 250 mL each! Understanding this relationship is the key to solving all problems in this chapter.

How to Convert Litres into Millilitres

1. Identify the Units — Look at the given measurement. Identify the part in Litres (L) and the part in Millilitres (mL). For example, in 3 L 250 mL, the Litre part is 3 and the Millilitre part is 250.
2. Multiply the Litres by 1000 — Since 1 L = 1000 mL, convert the Litre portion into Millilitres by multiplying it by 1000. For example: 3 L = 3 × 1000 mL = 3000 mL.
3. Add the Remaining Millilitres — Add the original Millilitres part to the newly converted value. For example: 3000 mL + 250 mL = 3250 mL.

Worked Examples on Volume and Estimation

• Example 1: A teapot contains 1 L 500 mL of tea. If 3 friends drink 250 mL of tea each, how much tea is left in the teapot? Step 1: Convert total tea to mL: 1 L 500 mL = 1500 mL. Step 2: Calculate tea consumed: 3 friends × 250 mL = 750 mL. Step 3: Subtract consumed tea from total tea: 1500 mL - 750 mL = 750 mL. Result: 750 mL (or 750 mL) of tea is left.
• Example 2: Anju wants to fill a 2 Litre water jug. She has a small glass of capacity 200 mL. How many times must she pour water from her glass to fill the jug? Step 1: Convert the jug's capacity to mL: 2 L = 2 × 1000 mL = 2000 mL. Step 2: Divide the total capacity by the glass capacity: 2000 mL ÷ 200 mL = 10. Result: She needs to pour water 10 times to fill the jug.

Watch Out for the Zero Trap!

A very common mistake students make is writing single-digit or double-digit Millilitres incorrectly when converting.

• Incorrect: 1 L 50 mL = 150 mL (This is wrong because 150 mL is less than even a quarter of a Litre!).
• Correct: Always remember that the Millilitre place must have three digits when writing combined units. Think of 50 mL as 050 mL. Therefore, 1 L 50 mL = 1000 mL + 50 mL = 1050 mL.

Always double-check your addition carefully!

Practice Questions with Solutions

• Q: Convert 5 L 8 mL into Millilitres. A: Step 1: Write down the conversion formula: 1 L = 1000 mL. Step 2: Convert the Litre part: 5 L = 5 × 1000 mL = 5000 mL. Step 3: Add the Millilitres part: 5000 mL + 8 mL = 5008 mL. Final answer: 5008 mL
• Q: Radha's water bottle holds 1 Litre of water. She drank 350 mL of water and her friend Mohan drank 400 mL. How much water is left in the bottle? A: Step 1: Calculate total water drank: 350 mL + 400 mL = 750 mL. Step 2: Convert the bottle's capacity to Millilitres: 1 L = 1000 mL. Step 3: Subtract the total water consumed from the bottle's capacity: 1000 mL - 750 mL = 250 mL. Final answer: 250 mL
• Q: A bucket holds 12 Litres of water. A small mug has a capacity of 400 mL. How many mugs of water are needed to fill the bucket completely? A: Step 1: Convert the bucket's capacity to Millilitres: 12 L = 12 × 1000 mL = 12000 mL. Step 2: Divide the total volume by the mug's capacity: 12000 mL ÷ 400 mL. Step 3: Simplify the division: 120 ÷ 4 = 30. Final answer: 30 mugs
• Q: A doctor advised Rohan to take 5 mL of cough syrup three times a day for a week. How many Millilitres of syrup will Rohan consume in 7 days? A: Step 1: Calculate the daily intake of syrup: 5 mL × 3 times = 15 mL per day. Step 2: Calculate the intake for a week (7 days): 15 mL × 7 days. Step 3: Perform the multiplication: 15 × 7 = 105 mL. Final answer: 105 mL

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