Today we will round very large and very small numbers.

round – to replace a number by another number of approximately the same value but having fewer digits: To the nearest dollar, the rounding of $27.68 yields $28.

very large numbers – numbers in the millions or higher; have 7 or more digits

very small numbers - numbers in the thousandths or smaller; thousandths are fractional parts of 1000

Concept

Molly has $16 in her pocket

She buys:

•3 hotdogs @ $1.89 each

•3 milkshakes @ $2.19 each

•3 Large French fries @ $ $1.79 each

Does she have enough money?

rounding

APK

to replace a number by another number of approximately the same value but

having fewer digits

TPS

very large numbersNumbers greater than 1 million

457,923,493

10,000,000,000,000

1,000,000

APKTPS

very small numbers

.5

5 tenths

numbers less than 1. They are represented by numbers to the

RIGHT of the decimal point. They are also called decimals.

.075

75 thousandthsAPK

TPS

decimal

.5

5 tenths

a number less than 1. It is represented by numbers to the

RIGHT of the decimal point.

.75

75 hundredthsAPK

When To RoundWhen the question asks:

– “Estimate how many…”– “About how many…”– Can you think of anymore?

Why is it important that we can round very large and very small numbers?

IMP

What are other reasons why it is important to know how to estimate very large and very small numbers?

Estimating is a great way to eliminate wrong answer choices

When we are asked for an estimate, this will help us figure out the answer quicker!

Let’s test the poem!The rounding poem

Find your number

Look right next door

4 or less, just ignore

5 or more add one more!

Rounding Whole Numbers

Round 474,000,000 to the closest hundred millions.

474,000,000 Find your number

Look right next doorFour or less, just ignore

Five or more, add one more

474,000,000 Rounded to the hundred millions becomes 500,000,000Round 474,000,000 to the closest 10 million’s

474,400,000

Just ignore – 470,000,000

What about decimal numbersThe same rules (and poem) apply!

Round 4.167 to the closest hundredths

4.167 Find your number

Look right next door4.17

RememberIf you are asked to round to the nearest tenth…….your answer

stops at the tenth place!

Example: Round 42.73 to the closest tenth would be 42.7

Special Case!Rounding a 9

Round 2.197 to the closes hundredths

Since there is a “9” in the hundredths place consider the

tenth and hundredths together – 19 – do you leave it at 19 or move

it to 20?

Round 4.95 to the closest tenth

Since there is a “9” in the tenth spot consider the ones

and tenths together…… should you leave it at 49 or

move it to 50?4.95 rounded to the nearest

tenth is 5.0

Let’s work some problems out together!

Steps1. Find your number

2. Look right next door

3. 4 or less, just ignore

4. 5 or more add one more!

125,345,878125,346,000

125,345,878125,000,000

125,345,878125,350,000

125,345,878100,000,000

987,565,484987,570,000

987,565,484987,565,000

987,565,48410,000,000

987,565,484988,000,000

Let’s work some problems out together!

Steps1. Find your number

2. Look right next door

3. 4 or less, just ignore

4. 5 or more add one more!

125.0238125.0

125.0238125.02

125.0238125.024

987.9655988.0

987.9655987.97

987.9655987.966

Let’s review!

• What does Rounding mean?

• What are very large numbers? Numbers in the millions or billions. Numbers like

2,304,000 and 2,455,098,098

What are very small numbers?Numbers smaller than one.Numbers like 0.456 and 0.4

Closure