**Category : **4th Class

**LEARNING OBJECITVES**

**This lesson will help you to:– **

- revise standard units of length like millimeter, centimeter and meter.
- choose appropriate standard unit of length.
- measure objects using standard unit of length. convert meter into centimeter.
- introduce standard units of weight like gram (gm) and kilogram (kg).
- choose appropriate standard unit of weight.
- weigh objects ' Jing standard units.
- convert the units of weight.
- introduce standard units of volume like litre (It).
- choose appropriate capacity of a container using standard unit of volume.
- convert the units of volume.

**Real Life Example:**

- Carpenter use measuring tapes to measure length of wooden furniture in order to construct them.
- Meters (m) are widely used in various races like car race, bicycle race etc.
- Knowledge of length helps us to construct rooms and buildings.
- Fruit sellers and vegetable sellers use weighing balance to weigh fruits and vegetables.
- Doctors weigh their patients before prescribing any medicine to them.
- Grocery store sells items like sugar, wheat flour (atta), tea etc. according to their weights.
- Cold drink bottles are f capacity 250ml, 300ml, 1litre, 2 litres, etc.

**QUICK CONCEPT REVIEW**

**LENGTH**

The standard unit for measuring length is a metre. The length of cloth, the height of a wall, the height of a tree, the distance between two objects are all measured in metres. Carpenters use measuring tape for making furniture, cloth merchant use a meter rod for measuring the length of clothes, measuring' tape is also used by tailors, masons etc. Metre is used to measure small distances.

**Conversion of units**

100 centimetres = 1 metre

100 cm = 1 m

We write 'm' for metre and 'cm' for centimeter. Smaller lengths are measured in centimeters. Sometimes smaller lengths are measured in decimeters. It is written as dm and is equal to 10 centimetres.

10 centimetres = 1 decimetres

10 decimetres = 1 metre

**Rule 1:** Multiply to change larger units to smaller units.

**Rule 2: **Divide to change smaller units to larger units.

** **

**Shortcut to Problem Solving tor Length**

- Always start from 0 while using measuring instruments.
- Millimeter (mm) and centimeter (cm) are used to measure small objects.
- Meter (m) is used to measure large objects.
- Meter (m) and kilometer (km) are used to measure large distances.
- Always convert the length of given objects into same unit of length before solving them.

**Historical Preview**

- It was the Greeks who developed the “foot” as their fundamental unit of length. It was based on an actual measurement of Hercules’ foot.
- The French created a standard unit of measurement called the metric system in 1790. This is today’s international system of unit for measurement.
- The gram was originally defined in 1795.
- The litre was introduced in France in 1795.
- Litre was named after a French wine merchant, Claude Emile Jean-Baptiste Litre.
- The word litre is derived from an older French unit, the ‘litron’.
- Archimedes discovered volume of solid objects using volume of water.

**Amazing Facts**

- You can measure you height using inches (inch) and feet (ft) also.
- One meter (m) is same as 100 centimeters (cm).
- One kilometer is same as 1000 meters (m).
- One kilogram is same as 1000 grams (gm).
- The human brain weighs about 1300 – 1400 gm.
- The body mass index (BMI) gauges you weight in relation to height.
- The base word litre is often spelled differently based on geography: litre is the favoured spelling in American English, while litre is used more often in European English.

**WEIGHT**

The standard unit for measuring mass or weight is a kilogram. We weigh things in kilograms. Lighter objects and smaller quantities of things are weighed in grams. We write kilogram as Kg and gram as g.

1 kilogram = 1000 grams

Or

1kg = 1000 g

We use balance and weights to weigh things.

** **

**Shortcut to Problem Solving for weight**

- Always start from '0' while using weighing balance.
- Gram (gm) is used to weigh lighter objects.
- Kilogram (kg) is used to measure heavier objects.
- Always convert the weight of given objects into same unit of weight before adding or subtracting them.

** **

**VOLUME (CAPACITY)**

The capacity of a container is the maximum amount of liquid which it can hold. The standard unit for measuring capacity is one litre. We measure liquids like water, milk and oil in litres. Small amounts of liquids like medicine are measured in milliliters. We write litre as 'I' and millilitre as 'ml'.

1 litre = 1000 millilitres

Or

11 =1000 ml

** **

**Shortcut to Problem Solving for Volume**

- Always use a container of capacity 1 litre to the capacity of other containers.
- To find the volume a liquid, just pour it to a container with a measuring scale marked on it.
- Millilitre is used to measure less quantity of liquids.
- Litre is used to measure greater quantity of liquids.
- Always convert the volume of given liquids into same unit of volume before adding or subtracting them.

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