These are of chapter 1 *Knowing our Numbers class 6 notes*. Hope you like these Knowing our Numbers notes and share the page among your friends.

- What are Natural numbers
- Comparison of Numbers
- Place Value of digit
- Estimation of the Numbers
- Roman Numerals
- Importance of Brackets

To find the place value of a digit in a number, multiply the digit with the value of the place it occupies.

1) If two numbers have unequal number of digits, then the number with the greater number of digits is greater.

2) If two numbers have equal number of digits then, the number with greater valued digit on the extreme left is greater. If the digits on extreme left of the numbers are equal then the digits to the right of the extreme left digits are compared and so on.

Here 4567 has four digits and 358 has three digits, so clearly 4657 is greater than 358

Here both the number have same digit, So we need start looking at the extreme left digit

1345 -> 1

2456 -> 2

Now 2 > 1

So we can clearly state 2456 > 1345

Here both the number have same digit, So we need start looking at the extreme left digit

4345 -> 4

4656 -> 4

As they are same, we need start looking at second extreme left digit

4345 -> 3

4656 -> 6

Now 6> 3

So we can clearly state 4656 > 4345

The arrangements of numbers from the smallest to the greatest is called ascending order.

The arrangement of numbers from the greatest to the smallest is called descending order.

Arrange the following in ascending order: 5392, 5782, 5789, 5654

The above rules of comparison can be applied here also.

Here all the number are of same number of digit and extreme left digit is also same. So we need to look at second extreme left digit

So 5782,5789 > 5654 > 5392

Now in 5782,5789, unit place makes the comparison easier

5789> 5782 > 5654 > 5392

So ascending order would be

5392 < 5654 < 5782 < 5789

Values of the places in the Indian system of numeration are Ones, Tens, Hundreds, Thousands, Ten thousands, Lakhs, Ten Lakhs, Crores and so on.

The following place value chart can be used to identify the digit in any place in the Indian system.

5,46,851 = 5 × 1,00,000 + 4 × 10,000 + 6 × 1,000 + 8 × 100 + 5 × 10 +1 × 1

This number has 1 at one’s place, 5 at tens place, 8 at hundreds place, 6 at thousands place, 4 at ten thousands place and 1 at lakh place.

Number Name are also written based on the place value name. So Its number name is Five lakh forty-six thousand eight hundred fifty-one

We can use below table format for easily reading and writing the Number

Commas added to numbers help us read and write large numbers easily. As per Indian Numeration, Commas are used to mark thousands, lakhs and crores. The first comma comes after hundreds place (three digits from the right) and marks thousands. The second comma comes two digits later (five digits from the right). It comes after ten thousand place and marks lakh. The third comma comes after another two-digits (seven digits from the right). It comes after ten lakh place and marks crore

1, 08, 01, 992

2, 32, 40, 581

3, 17, 05, 062

Values of the places in the International system of numeration are Ones, Tens, Hundreds, Thousands, Ten thousands, Hundred thousands, Millions, Ten millions and so on.

1 million = 1000 thousands,

1 billion = 1000 millions

Following place value chart can be used to identify the digit in any place in the International system.

As per International 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. For example, the number 10,101,592 is read in the International System as tem million one hundred one thousand five hundred ninety-two. In the Indian System, it is 1 crore one lakh one thousand five hundred ninety-two.

A reasonable guess of the actual value is called an estimate.

A quick, rough estimate of the result of number operations can be done by rounding off the numbers is involved.

1)Estimating numbers to the nearest tens is done by rounding off numbers 1, 2, 3 and 4 to 0 and number 6, 7, 8, 9 to 10.

2) Estimating numbers to the nearest hundreds is done by rounding off numbers 1 to 49 to 0 and numbers 51 to 99 to 100.

3) Estimating numbers to the nearest thousands is done by rounding off numbers 1 to 499 to 0 and the numbers 501 to 999 to 1000.

Estimation involves approximating a quantity to an accuracy required. We can apply the above rules depending on the accuracy required.

We can estimate Sum, difference and Multiplication by applying the rules of estimation also. We can apply the above rules depending on the accuracy required and how quickly answer can be find out

Roman Numerals system is another system used apart of Hindu-Arabic system.

The Roman numerals are

I |
1 |

II |
2 |

III |
3 |

IV |
4 |

V |
5 |

VI |
6 |

VII |
7 |

VIII |
8 |

IX |
9 |

X |
10 |

X1 |
11 |

X11 |
12 |

XX |
20 |

L |
50 |

C |
100 |

D |
500 |

M |
1000 |

1) In Roman numerals a symbol is not repeated more than three times, but the symbols V, L and D are never repeated.

2) Roman numerals are read from left to right and the letters of Roman numerals are arranged from the largest to the smallest.

3) If a symbol of smaller value is written to the right of a symbol of greater value, then its value gets added to the value of greater symbol.

VI = 5 + 1 = 6

4) If a symbol of smaller value is written to the left of a symbol of greater value, its then value is subtracted from the value of the greater symbol.

IV = 5 – 1 = 4

5)The symbol I can be subtracted from V and X only.

The symbol X can be subtracted from L, M and C only.

Brackets help in simplifying an expansion with more than one mathematical operation.

In an expression that includes brackets, the numbers inside the brackets must be simplified into a single

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Class 6 Maths Class 6 Science