Q) How many sharpeners are there in the below image?

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Q) Lengths Which is measured using Hand is called?

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Q) Lengths Which is measured using Foot is called?

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Q) When the pans balance, the weight on both the pans is what?

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Q) Look at the glass and write the glass which contains more water ?

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Q) Write the length of the scissors ?

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Q) How much quantity of water required to our body per a day ?

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Q) Liquids is measured in What?

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Q) What is the name of below measure ?

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Q) What is the name of below measure ?

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Q) Which is the biggest building of these two buildings?

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Q) Which is the highest pans in these two pans?

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Q) Write the length of the pencil ?

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Q) Write the heavier animal in both of these ?

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Q) What is the name of below measure ?

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the action of measuring something. The size, length, or amount of something, as established by measuring. It is a unit or system of measuring.

We use scale to measure small lengths. We use a measuring tape to measure bigger lengths.

For example, a hockey stick is about 1 meter long.

Centimeter,meter, and kilometer are the most used units of length.

- measuring cylinders to measure the volumes of liquids such as kerosene, milk, oils, water, etc.
- The volume of liquids is expressed in liters (l) or millilitres (ml).
- It is cylindrical in shape, with graduations marked on its body.
- Measuring cylinders are available in different sizes.
- They are used in laboratories to measure a certain volume of a liquid and to measure milk, oils, etc by shop keepers.
- We can fill it with the liquid to be measured and then read the marking at the lowest point of the concave surface of liquid.

**Measuring cylinder**

- Apart from measuring the volumes of liquids, we also measure the volumes of solids, for example, loose solids like sand, clay, and ready mix of cement.

Measure the length of one side of a table using your hand-span. Askyour classmates to do the same.Record the length of the table in terms of number of hand-spans table

We do not get the same measurements in two cases mentioned above because the hand-spans / foot-spans are not same for each one of us. We often use these type of conventional methods to measure certain lengths. For example, cubits for the length of a string of flowers and length and breadth of a playground using strides. Similarly, we use this system of measurement while playing 'sirra gona', (gilli danda), where the length of the stick is used as the unit to measure the desired distance.

Many hundred years ago, people used to measure distances with their hand spans, strides or foot-spans. One day a very tall man went to a shop to buy some cloth. He asked for three-and-a half arms length of cloth. The shopkeeper measured three arm lengths of cloth and then added approximately another half-arm length.

The man felt that the shopkeeper had cheated him. So he measured the cloth with his arms and found that the cloth was not even three arm lengths. He told the shopkeeper that the length of the cloth was less than three-and-a-half arms when he measured with his own arm. The shop keeper replied that his own arm was the standard for measuring. They both argued about whose arm was to be taken as standard measure. In those days, people arguing over measuring the length of fields, ropes, and hundreds of other things must have been a familiar fight. How should one measure a half or a quarter arm length?

Finally, some sensible people got together and decided to have a scale of a fixed length. In order to measure subunits, they marked this scale with several smaller but equal divisions. They then decided that everyone would measure lengths with this scale. They used wood and metal to make scales of the same length.

At one place, people decided to use the distance between the nose and the tip of the middle finger of their king as a measure.They called this distance one yard. They used wood and metal to make scales of this length and called this distance one yard. This yard was divided into three equal parts and each part was called a foot. They then divided each foot into twelve equal parts called inches. They even divided each inch into smaller segments!

Other countries in the world also made their own scales. Because each country had its own scale which differed from others, it led to a lot of problems in trade and commerce. There was always a chance of quarrels breaking out.

Finally in France, it was decided that a certain length of rod made of a special material (Platinum-Iridium) would be called a meter. The meter was divided into 100 equal parts and these parts were called centimeter. Each centimeter was further divided into ten equal parts called millimeter. Now we are using this as a standard measurement for length throughout the world. This original scale is preserved in a museum in France.

The story explains the need of standard instruments to measure lengths. The meter scale is internationally accepted instrument for measuring lengths.

One meter is a standard unit of length.

We use meter as a unit of length and subsequently, centimeters and millimeters as smaller units of length.

In our daily life, we use different instruments like plain tape, rolled tape, centimeter scale of different sizes, made up of wood, metal or plastic.

If you want to measure the thickness of an eraser, which of the instruments shown is more suitable and why?

Sometimes we may need to measure long distances like length and breadth of school play ground or agricultural fields or distance between our house to school, distance between one town to another town, and even longer distances such as those between one country and another country.

Meter is not a convenient unit for measuring large distances. We need to define a larger unit to measure larger distances. We use kilometer as a larger unit of length. One kilometer is 1000 times longer than a meter.

- Take a measuring cylinder and fill almost half of it with water.
- Record the volume of water. Let us assume it is "a" cm3 (or "a" ml).
- Now tie a small irregular solid (stone) with a fine cotton thread.
- Put the solid gently into the water in the cylinder so that it is completely immersed in water.
- What changes do you notice in the water level of the cylinder?

- You may notice that the level of water in the measuring cylinder rises as the stone displaces water equal to its own volume.
- Record the new volume of water.
- Let us assume that it is "b" ml.
- Now the volume of stone will be the difference between the second volume and the first volume i.e volume of the stone = (b - a) cm3.

- Ask your classmate to stand with his/ her back against a wall.
- Make a mark on the wall exactly above his/her head. Now measure the distance, from the floor to this mark on the wall, with a scale.
- Let all other students measure this length in a similar way.
- Record your observations in your notebook.
- Study carefully the measurements reported by different students.

- Do you all have the same readings of measurements?
- If not, what could be the reason for the differences?
- In the above activity, though the measurement was done using a standard scale, results may be close to each other but not exactly equal.
- The difference in reading is due to some errors in measurement.
- Not marking the point exactly at the top of the head.
- Not using the metre scale in a proper manner.
- To measure the lengths accurately using the standard measuring instruments like meter scale, centimeter scale and tape etc.

- Let us find out the area of a surface, say a banana peel or a leaf, which has irregular shape.
- Place the leaf on a graph paper . Mark the boundary of the piece of leaf on the graph paper with a pencil.
- Now remove the leaf to find the outline or boundary of the leaf on graph paper.
- Count the number of complete squares (each of 1 cm2 area) inside the boundary.
- Also count those squares, inside the boundary, which are half or greater than half.
- Add this to the number of complete squares. This total number of squares inside the boundary gives the area of the leaf.
- If there are 'n' squares inside the boundary, the area of the leaf becomes n cm2.
- Neglect those squares, inside the boundary, which are less than half.
- This process will gives us the value of area which is close to the actual area.

- Cut a cardboard into a shape of rectangle having length 4 cm and breadth 2 cm .
- Let us measure its area.
- The convenient unit to measure the area
of given cardboard would be cm
^{2}. - Take a centimetre graph paper. Each small square on this graph paper has a side equal to 1 cm.
- The area of each
small square on this graph paper is 1
cm
^{2}. - Place the cardboard on the centimetre graph paper and draw its outline with the help of a sharp pencil. Now remove the cardboard and mark the shape as PQRS.
- Count the number of squares inside the outline.
- The number of squares is 8.
- Area of the cardboard is equal to the area covered by PQRS on the graph paper.
- Area of PQRS = Total area of
unit squares
inside the PQRS

= 8 × area of 1 unit square

= 8 × 1cm^{2}

= 8 cm^{2}

In this case, the cardboard we used has a regular shape - rectangle