• number notation and place values (ten thousands, thousands, hundreds, tens, ones)

• rounding off numbers to the nearest

10 or 100

• use of the approximation

symbol (≈)

What will we learn today?

Whole Numbers Numbers up to 100 000

Understanding the place values

Before we begin, let’s understand what is place values.

In the number 1245,

tens ones

In the number 1245,

thousands hundreds

81245

thousands hundreds

In a 5 digit number

ten thousands

In a 5 digit number

81245

So, in a 5-digit number,

There are

Ten thousands place

Thousands place

Hundreds place

Tens place

Ones place

Here’s an example.

In 9265, the digit 2 is in the ___ place.

a) ones

b) tens

c) hundreds

d) thousands

In 9265, the digit 2 is in the ___ place.

a) ones

b) tens

c) hundreds

d) thousands

The ‘2’ stands for 200.

In 9265, the digit 2 is in the ___ place.

a) ones

b) tens

c) hundreds

d) thousands

Here’s another example.

In 27501, the digit 5 stands for _____.

a) 5

b) 50

c) 500

d) 5000

In 27501, the digit 5 stands for _____.

a) 5

b) 50

c) 500

d) 5000

The ‘5’ is in the hundreds place.

In 27501, the digit 5 stands for _____.

a) 5

b) 50

c) 500

d) 5000

The ‘5’ stands for 500.

rounding off numbers to the nearest 10 or 100, and learn the use of the approximation symbol (≈)

Let’s try:

Rounding off Numbers

Look at the digit to the right of the required place value.

– If the digit is less than 5,

round down.

– If the digit is 5 or more,

round up.

Try this out!

Round off 483 to the nearest hundred.

Solution

1) Round off 483 to the nearest hundred. Answer:500 (8 is more than 5 so we round up)

To round off a number correct to a given place, we round up (that is add 1) if the next figure is 5 or more, we round down (that is just drop them) if the next number is less than 5.

Here’s an example.

Try this out!

Round off 314 to the nearest hundred.

Try this out!

Round off 314 to the nearest hundred.

3 | 14 ≈ 300

1 is less than 5, so we just drop 14. That is why we round down to 300.

You have done a great job! Let’s move on!

What is the best estimate for 589 x 61 ?

(1) 500 x 60

(2) 500 x 70

(3) 600 x 60

(4) 600 x 70

What is the best estimate for 589 x 61 ?

(1) 500 x 60

(2) 500 x 70

(3) 600 x 60

(4) 600 x 70

589 ≈ 600

Let’s try rounding off the number.

What is the best estimate for 589 x 61 ?

(1) 500 x 60

(2) 500 x 70

(3) 600 x 60

(4) 600 x 70

61 ≈ 60

Let’s try rounding off the number.

What is the best estimate for 589 x 61 ?

(1) 500 x 60

(2) 500 x 70

(3) 600 x 60

(4) 600 x 70

Compare your answers with the given option

589 ≈ 600

61 ≈ 60

What is the best estimate for 589 x 61 ?

(1) 500 x 60

(2) 500 x 70

(3) 600 x 60

(4) 600 x 70

Compare your answers with the given option

589 ≈ 600

61 ≈ 60

Are you ready to try out the questions?