Chapter-5

Far and Near
We have learnt about measuring length and some standard units we use to measure length. In this chapter we will learn some more units of measuring distances and the relationships between different units.
Let Us Find
Identify the appropriate units for measuring each of the following.
| Quantity | Unit of measurement Metre (m) or centimetre (cm) |
|---|---|
| Height of India Gate | 42 |
| Length of a handkerchief | 40 |
| Depth of a well | 50 |
| Length of a mobile phone | 13 |
| Length of an elephant's trunk | 2 |
| Distance between two buttons on a shirt | 5 |
Different Units but Same Measure
Shikha and Sonu are measuring the lengths of saris and stoles in the village weaving centre. Find which measures represent the same sari or stole. You can take help of the double number line below.
| 204 cm | 5 metre 40 cm |
| 540 cm | 2 metre 204 cm |
| 750 cm | 2 metre 4 cm |
| 240 cm | 2 metre 40 cm |
| 404 cm | 6 metre 150 cm |
Let Us Compare
1. Ritika is comparing the lengths of different rods. Compare them using <, =, > signs.
- (a) 456 cm โโโโโโโโ 5 m
- (b) 55 cm + 200 cm โโโโโโโโ 200 cm + 54 cm
- (c) 6 m 5 cm โโโโโโโโ6 m 50 cm
- (d) 2 m 150 cm โโโโโโโโ3 m 50 cm
- (e) 238 cm โโโโโโโโ138 cm + 1 m
2. World's tallest statue
(a) What is the difference between the height of the tallest statue in the world and the Statue of Liberty?
(b) Identify the statues whose heights have the least difference.
(c) Identify the statues whose heights have the largest difference.
(d) The height of which statue will be equal to the height of the Statue of Unity, if it is doubled?
Measuring Long Distances
Here are some ways in which you can measure long distances.
Let Us Do
Measure 100 m and 200 m on your school playground, or any other place in and around your school, using a Long Tape. Mark these points and draw a straight line. Walk on the lines and count the number of steps. Use this relationship between the number of steps taken and distance walked to find distances around you for at least 3 locations. Wherever possible, walk and find the number of steps. Otherwise, find the distance and estimate the number of steps.
(a) Identify and write the locations that are the nearest and the farthest from your home.
Nearest location---------------------Farthest location---------------------
(b) Write the distances obtained above in increasing order. ------------ , -----------, -----------, -----------
(c) Name a location that is equal to or more than 1,000 m from your home.
Let Us Explore
When we walk 1,000 m, we say we have walked 1 km.
1,000 m = 1 km| Length of rope | Number of ropes needed to make 1 km |
|---|---|
| 1000 m | 1 |
| 100 m | |
| 10 m | |
| 200 m | |
| 500 m | |
| 250 m |
Kilo stands for thousand. This unit is used to measure long distances.
Kilometre Race
Sheena and Jennifer are helping to organise a 3-km race. Help them with the arrangements for the race.
1. Water stations are to be arranged after every 500 m. How many water stations must be set up? At what positions from the starting point will these water stations be placed?
2. Children need to stand at an interval of 300 m to direct the runners. How many children are needed? At what positions from the starting point will the children be standing?
3. Red and blue flags are to be placed alternately at every 50 m. How many red and blue flags are needed till the finish line?
Let Us Do
Longest Train Journey
The longest train journey in India is by The Vivek Express which runs from Dibrugarh in Assam to Kanniyakumari in Tamil Nadu. Look at the stations on the route shown in the table below and answer the questions.
| Station number | Name of the station | Distance from Dibrugarh |
|---|---|---|
| 9 | Dimapur | 306 km |
| 14 | Guwahati | 556 km |
| 22 | Jalpaiguri Road | 983 km |
| 34 | Bhubaneswar | 2,007 km |
| 40 | Visakhapatnam | 2,450 km |
| 45 | Vijayawada JN | 2,800 km |
| 55 | Coimbatore JN | 3,675 km |
| 65 | Kanniyakumari | 4,187 km |
- 1. The total length of the route from Dibrugarh to Kanniyakumari is ........km.
- 2. The distance between Vijayawada and Jalpaiguri road is.......
- 3. Distance between Vijayawada and Visakhapatnam is.........
- 4. Which two stations are farther apart-Guwahati and Dimapur or Bhubaneswar and Jalpaiguri Road?
- 5. What is the distance between Guwahati and Coimbatore JN?
Let Us Explore
The World of Small Things
How can we measure small things like the ones shown here?
Let us look at the scale. Do you notice the small marks between 1 cm and 2 cm? Count how many marks are there between 1 cm and 2 cm?
One centimetre is divided into ten equal parts. Each part is called 1 millimetre (mm).
1 cm = 10 mm
1 cm 10 mm
These small marks between any two centimetre marks help us measure the smaller lengths. Thus, it adds to the precision in measurement.
Let Us Measure
Measure the lines in the design and write their measurements in cm and mm.
Let Us Do
Soak some seeds of whole moong or black or white chana overnight. Next morning, take them out and wrap them in a moist cloth to sprout them. Over the next 4 days, take out one seed each day and measure the length of sprout. For ease of measurement, you can either place the seed on a paper and mark the length of the sprout, or use a thread to find its length.
| Number of days | Length of the sprout (in mm) |
|---|---|
| Day 1 | |
| Day 2 | |
| Day 3 | |
| Day 4 |
Let Us Draw
Draw lines of the following lengths in your notebook using a scale.
- 1. 5 cm 5 mm
- 2. 3 cm 6 mm
- 3. 8 cm 3 mm
- 4. 36 mm
- 5. 67 mm
How did you draw lines of lengths 36 mm and 67 mm? Share your thoughts in class.
Relationships between Different Units
100 cm = 1 m
1,000 m =1 km
Let Us Do
1. Fill in the blanks appropriately in the double number lines given below.
2. Use your understanding from above to fill in the blanks appropriately.
- (a) 4 cm 5 mm = ______ mm
- (b) 89 mm = ____ cm ____ mm
- (c) 234 cm = ____ mm
- (d) 514 mm = ____ cm ____ mm
- (e) 6 m 34 cm = ____ cm
- (f) 20 m 12 cm = ____ cm
- (g) 397 m = ______ cm
- (h) 5,792 cm = ______m ____ cm
- (i) 9,108 cm = ______ m ______ cm
- (j) 34 km = _______ m
- (k) 6,870 m = ____ km ____ m
- (l) 10,552 m = ____ km ___ m
- (m) 29 km 30 m = ____ m
- (n) 32 km 359 m = ____ m
Adding and Subtracting Lengths
saji saw on his smartphone that he walked 3 km 450m in the morning and another 4 km 650 m in the evening. How much did he walk in the whole day? How would you solve this problem? Share your thoughts in class.
Electricians are changing the cables in a house. They need 63m of cable for this purpose. They used 16m 75cm cable in the first room. What is the length of the cable left?
Therefore, 46 m 25 cm cable is left.
Let Us Do
1. Rani has two red-coloured ribbon rolls, one of length 3 m 75 cm and another 2 m 25 cm long. How much ribbon does she have?
2. The distance from Bhopal to Sanchi is 48 km 700 m. Bhadbhada Ghat waterfall is on the way, and 17 km 900 m away from Bhopal. How far is Sanchi from the waterfall?
3. Gulmarg Gondola in Gulmarg, Kashmir is the second longest and second highest cable car in the world. It is divided into two sections. The first section covers 2 km 300 m and the second section covers 2 km 650 m. What is the total distance covered by the cable car?
4. Circle the bigger length and find the difference.
| (a) 11 mm and 1 cm | Difference-โโโโโโ |
| (b) 26 mm and 2 cm | Difference-โโโโโโ |
| (c) 20 cm and 201 mm | Difference-โโโโโโ |
| (d) 1,020 mm and 1m | Difference-โโโโโโ |
| (e) 2 m and 245 cm | Difference-โโโโโโ |
| (f) 5,678 m and 6 km | Difference-โโโโโโ |
| (g) 6 km 1,480m and 7 km 479m | Difference-โโโโโโ |
Multiplying and Dividing Lengths
1. We need a 1 m 80 cm cloth to make a shirt for a 10-year old child. How much cloth will be needed to make shirts for 20 such children?
20 x 1 m 80 cm = 20 x 1 m and 20 x 80 cm
=20 m + 1600 cm
Break the quantity into m and cm and multiply. You can also convert it into cm and multiply.
= 20 m + 16 m
= 36 m.
2. A shop sells cloth for making bags at โน100 for 5 m. How much money is needed to buy a 1 m cloth?
If 5 m cloth costs โน100, then a 1 m cloth costs 100/ 5 = โน20.
Now, use the double number line to find the cost of the cloth or the length of cloth that we can buy at a particular cost.
3. Anita is making an embroidery on the border of a sari. She needs a 1 m long thread to embroider a 50 cm sari. How much thread would she need for a 5 m sari border?
A 1 m long thread costs 50. How much money will be needed to buy the thread?
4. A road 12 km 600 m long is being laid in a town. The workers lay an equal length of road each day, and complete the work in 6 days. How much road-laying work is done on each day?Let Us Estimate
Estimate the following. Share your reasoning in class.
1. The height of the tallest building in your neighbourhood. What did you use as a reference to estimate the height?
2. The height of the tallest tree in your neighbourhood. What did you use as a reference?
3. The depth of a well or swimming pool in your neighbourhood. How did you find out?
Let Us Explore
In daily life, we use other units of measuring length as well. Height is usually measured in feet and inches. Look at your ruler to see if inches are also marked on it. Find out how many cm and mm equal 1 inch.
1 inch = 2 cm 5 mm1 foot = 12 inches or 30 cm.
Measure Your Height
Stand against a wall and mark your height. Measure the distance between the floor and the marked point in feet and inches.
Similarly, other students in the class can also measure their heights.
Find out who is the tallest student in your class. What is his or her height in feet and inches?