Its for 6th to 8th grades students. Students will like this ppt.

1. Class: 6
Subject: Mathematics
Topic: Knowing our numbers

2. • Introduction of
topic by asking
questions, and
recap
• Use of
commas and
Number
system
• Estimation of
numbers
• Estimation
nearest 10s,
100s and
1000s
• Number
situation
• Activity on
estimation by
doing school
survey
• Assessment
on estimation
• Assessment
on number
situation
• Key terms
are added at
the end of the
lesson

3. Teacher Notes
• Ask students to read large numbers using the Indian
system
• Introduce the chapter by asking known question related to
Comparing numbers, large numbers
• Relate the questions and answers to the introduce the topic
• Students should be able to recall the previous knowledge
about Indian number system

4. Commas
• The second comma comes two digits later (five digits
from the right). It comes after ten thousands place and
marks lakh.
485 , 38,621
4 , 85,38,621
• The third comma comes after another two digits(seven
digits from the right).It comes after ten lakh place and
marks crore.

5. International System of Numeration
• In the International System of Numeration, we have
ones, tens, hundreds, thousands and then millions.
• One million is a thousand thousands.
1 million =1000000

6. International System of Numeration
• Commas are used to mark thousands and millions. It
comes after every three digits from the right.
• The first comma marks thousands and the next
comma marks millions.
57,346,678
Fifty seven million, three hundred and forty
six thousand, six hundred and seventy six

7. Teacher Notes
• In the following slide, show the video to students
• Ask them to observe
– Indian number system
– International number system
• Ask them to carefully understand differences between two number
system
• After the video ask them to answer the questions in the following
slide
• Explain basic metric conversion

8. Difference between two number system

9. • How many lakhs make a million?
• How many millions make a crore?
1 billion = 1000 million.
How many zeros are there in a billion?
10 lakhs
10 million

10. Large numbers in Practice
mm
cm
m
km
Millimetre
Centimetre
Metre
Kilometre
Divide by 10
Divide by 1000 Divide by 100
multiply by 1000 multiply by 100 multiply by 10

11. Large numbers in Practice
• To convert from a LARGER unit to a SMALLER unit...MULTIPLY
• To convert from a SMALLER unit to a LARGER unit...DIVIDE
Kilo Centi Milli

12. Conversion table
Weight Length Capacity
Kilogram(kg)
1000 gm
Kilometre(km)
1000 m
Litre(l)
1000ml
Gram(gm)
1000 mg
Metre(m)
100 cm,
1000 mm
Centimetre(cm)
10 mm
Milligram(mg) Millimetre(mm) Millilitre(ml)

13. Weight Length Capacity
Kilogram(kg)
1000 gm
Kilometre(km)
1000 m
Litre(l)
1000ml
Gram(gm)
1000 mg
Metre(m)
100 cm,
1000 mm
Centimetre(cm)
10 mm
Milligram(mg) Millimetre(mm) Millilitre(ml)
How many millimetres are there in 1 kilometre?
How many centimetres are there in 1 kilometre?

14. Lalita bought 3 m of cloth. She needs cut it into pieces of
75 cm each. How many pieces will she be able to cut?
STEP 1- Convert 3m to cm =3x100 cm =300 cm
STEP 2- Divide 300 cm by 75 cm, 300/75= 4
STEP 3- Lalita will be able to cut 4 pieces of 75 cm each.

15. Let us find out….
• How many people are there in your village/City?

16. Introduction
• Are the answers same from all the students?
• Do the answers give the exact numbers?
• Can we finalize the answers given by students as correct
numbers?
To answer such questions we use approx., nearly and
roughly calculated number.

17. Estimation
• How many people are there in your village/City?
Assume that there are roughly 90000 people in your city

18. When we say 90,000 people, It can be 85167 or 91548,
it may be little less or more, but not exact numbers
This is called Estimation.
This can be done by rounding of the number to the
nearest tens, hundreds or thousands…etc.

19. Estimation
• Estimation is done to express amounts of money,
duration, distances, and many other physical quantities.
• Rounding off is a kind of estimating.

20. Teacher Notes
• Ask the students to do a school survey as a part of the activity
• Divide the students into groups
• Ask students to find out usage of water at home
• Tell them that approximately 10 mugs of water will make one bucket.
• Ask them to find out the usage of water at home for one person .
• Ask students to take average.Ask each group to explain the approximate
usage of water.
• Explain to students how one could use approximation in their daily life
• The following slides explain the approximation in numbers.
(Teacher could also talk about conserving water.)

21. Estimation-Nearest tens
Lets see an example rounding off to the nearest tens.
20 21 22 23 24 25 26 27 28 29 30
21 is nearest to 20 than 30. So 21 is rounded off to 20
26 is nearest to 30 than 20. So 26 is rounded off to 30

22. Estimation-Nearest tens
Lets see an example rounding off to the nearest tens
323 is nearest to 320 than 330. So 333 is rounded off to 320
327 is nearest to 330 than 320. So 327 is rounded off to 330
320 321 322 323 324 325 326 327 328 329 330

23. Estimation-Nearest tens
Lets see an example rounding of to the nearest tens
2342 is nearest to 2340 than 2350. So 2342 is rounded off to 2340
2346 is nearest to 2350 than 2340. So 2346 is rounded off to 2350
2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350

24. Estimation-Nearest hundreds
To estimate nearest hundreds of any number, we need to
examine the last two digits of that number.
478
448 is between 400 and 500 48 is closer to 0
than to 100
is between 400 and 500 78 is closer to 100
than to 0

25. Estimation-Nearest hundreds
It is easier to examine the tens place of that digit.
478 500
448 400
Is the number at tens place greater
than 5?
No.
Replace tens and ones place with 0
Is the number at tens place greater than
5?
Yes.
Replace tens and ones place with 0.
Increase the digit at hundreds place by 1

26. Estimation-Nearest Thousands
To estimate nearest thousands of any number, we
need to examine the last three digits of that
number.
2345 2000
2647 3000
345 is closer to 0 than 1000
345 is closer to 1000 than 0
Can you tell an easy method?

27. Estimate- Outcomes of number situation
• We know that we add numbers by following the
algorithm systematically. Like,
5 3 4
2 7 1
5
0
8
1
+
While adding the numbers, we first add the digits in units place and carry
appropriate numbers if necessary to the adjacent units place.

28. Estimate- Outcomes of number situation
Estimation helps to get answers quickly.
Radha has Rs.11,000 in her hand and she needs to pay
Rs.7890 at the grocery shop and Rs.2,280 at the milk shop.
Do you think Radha will have enough money?

29. Summary
• While adding the numbers, we first add the digits in units place and
carry appropriate numbers if necessary to the adjacent units place.
• To estimate nearest hundreds of any number, we need to examine
the tens place of that digit is more than or less than 5.If it is less than
5 then we replace tens and ones place with 0 else we add 1 to the
hundreds place and replace ones and tens place with 0

30. Summary
• To estimate nearest thousand of any number, we need to examine
the hundreds place of that digit is more than or less than 5.If it is
less than 5 then we replace hundreds ,tens and ones place with 0
else we add 1 to the thousands place and replace ones, tens and
hundreds place with 0
• When you want to round off a number, underline the digits starting
from the place you want to round off to. This makes it easier to see
the relevant digits to change.

31. Assessments

32. Practice 1
• Write the following in figures in the International system:
– Three hundred and twenty-five thousand, four hundred and two
– 25212423 add commas according to international system
– Four million, one hundred and thirty-two thousand, three
hundred and sixteen
325,402
4,132,316
25,212,423

33. Practice 2
– 315,121,810
– 25,212,423 add commas according to Indian system
and write in words
Three hundred and fifteen million, one hundred and
twenty-one thousand, eight hundred and ten
2,52,12,423 Two crore, fifty two lakhs, twelve
thousand, four hundred and forty three

34. Practice 3
Round off to nearest hundred:
1. 3456
2. 9843
3. 78235
4. 340
3500
9800
78200
300

35. Practice 4
Meena has 4 litres and 500 millilitres of milk . She has to
distribute this to 9 people equally. How much will each
person get?
Answer- 500 ml

36. Key Terms
• Estimation
• Roughly
• Approximately
• Nearly

37. References
• https://www.youtube.com/watch?v=6rk4OiXx9i8
(Difference between Two number system)