## Number Sense

Category : 2nd Class

LEARNING OBJECTIVES

• learn about numbers greater than 99.
• study about ones, tens, hundreds of a number.
• learn about the place value and expanded form of a number.

QUICK CONCEPT REVIEW

In the previous class, we have learnt about numbers upto 99.

Let us now learn about numbers greater than 99.

We know that 99 is the largest 2-digit number. When we add 1 in 99 it will become 100.

99+1 = 100

100 is the smallest 3 digit number.

BUILDING NUMBERS UPTO 200

Let us understand how to make numbers greater than 100 by taking following example:

Raghu works in the post office, selling stamps.

This is one stamp.

This is a strip of 10 stamp.

This is a sheet of 100 stamp. On adding one more stamp to these 100 stamps it will become 101 stamps. This is how Raghu counts stamps more than one hundred. And we say this is one hundred one

$100+1\xrightarrow{{}}101\,\,\begin{matrix} H & T & O \\ 1 & 0 & 1 \\ \end{matrix}$

2 more stamps in 100 stamps will form 102 and we say as one hundred two.

PLACE VALUE OF A NUMBER

The value of a digit due to its position in a number is called its place value.

Three digit numbers have three place values-ones, tens, hundreds.

We write it as 206 and read it as two hundred six.

Let us take an example:

3 - This number has one digit

26 - This number has two digit

165 - This number has three digit

Digits 3. 6, 5 in numbers 3, 26,165 are all in the ones place respectively.

2 in number 26 and 6 in number 165 are in the tens place. The place value of 2 in 26 is 20.

1 is in hundreds place in 165. The place value of 1 in 165 is written as 100.

NUMBER NAME

How can we read a number?

To read a 3-digit number, first read the hundreds place and then read the last two digit together.

For example:

1 0 5 One hundred five

FORMING NUMBER

How numbers are formed? Let us understand this with the help of some examples.

 H T O 1 2 6

We write it as 126 and read it as two hundred six.

2.

 H T O 1 6 2

We write it as 162, we read it as one hundred sixty two.

NEAREST NUMBER

Now, lets us discuss about nearest number by taking some examples:

If we want to find nearest 10 of the number 68 then 70 will be the answer. But if we have the numbers like 61 or 62 then their nearest ten is 60 and in case of 65 the nearest ten is 70. This is because when number at ones place is less than 5, as in 61 or 62 than nearest ten will be 60 but if number at ones place is 5 or greater than 5 than we take 70 as the nearest ten.

For three digit numbers, if we want of find the nearest hundred we consider the number at tens place. For example, for 245, nearest hundred will be 200 as the number at tens place is 4, which is less than 5 and nearest hundred of number 255 or 265 will be 300, due to presence of number 5 or greater than 5 at tens place.

EXPANDED FORM

When we add the place value of all the digits in a number, then we get the expanded form of that number.

Let us take an example:

The number 175 has 1 hundred + 7 tens + 5 ones = 100 + 70 + 5

This is the expanded form of 175.

Let's make it clear with a few more examples.

1. 206=200+6

2. 467=400+60+7

Historical Preview

• The numerical digits we use today as 1, 2 and 3 are based on the Hindu Arabic numeral system developed over 100 years ago.
• The equal sign (=) was invented in 1557 by a welsh mathematician named Robert Recorded.

Amazing Facts

• Different names for the number ‘0’ include naught, nil and zip.
• The number 5 is pronounced as ‘Ha’ in Thai language.
• ‘Four’ is the only number in the English language that is spelt with the same number of letters as the number itself.

Real Life Examples

• Numbers help us calling a friend using mobile phones.
• Number help us in checking the price of an item.

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