How do I round 24,972 to the leading digit?

l l l l l l l l l l l20,000 30,00024,972

or

Midpoint

In this lesson you will learn how to round numbers to the

leading digit by using a number line.

Let’s ReviewLet’s Review

Leading Digit - The digit at the beginning of a number.

For example:687

5,924832,605

Let’s ReviewLet’s Review

Rounding - To find a number that is close to a given number.

l l l l l l l l l l lBakery

Morgan

Ashley Pizza

Let’s ReviewLet’s ReviewReading a Number Line

l l l l l l l l l 10 20 11 12 13 14 15 16 17 18

19 l l l l l l l l l 100 200 110 120 130 140 150 160 170 180

190 l l l l l l l l l

1000 2000 1100 1200 1300 1400 1500 1600 1700 1800 1900

Let’s ReviewLet’s Review

l l l l l l l l l l l783700 800

Benchmark Numbers

Midpoint

750

Let’s ReviewA Common Mistake

Thinking that the increments on a number line always signify counting by

ones.

l l l l l l l l l 300 400 310 320 330 340 350 360 370 380 390

Let’s ReviewA Common Mistake

Misapplying the concept of “rounding down”.

For example:4,392 = 3,3924,392 = 4,000

Let’s ReviewCore Lesson How can I use benchmark numbers and midpoints to help

me round?

l l l l l l l l l l l5000 60005500

Numbers less than the midpoint round down.

Numbers the same as or greater than the midpoint round up.

Let’s ReviewCore Lessonl l l l l l l l l l l

5000 60005500

5000 6000

55005001 - 5499 5500 - 5999

Let’s ReviewCore Lesson

Round 342,789l l l l l l l l l l l

300,000 400,000

Benchmark Numbers

Midpoint350,000

Let’s ReviewCore Lesson

Round 28,012l l l l l l l l l l l

20,000 30,000

Benchmark Numbers

Midpoint25,000

Let’s ReviewCore Lesson

Round 33,786 to the nearest ten thousand.

30,000All of the digits

behind the 3 turn to 0.

30,000 is the closest

benchmark number.

Let’s ReviewCore Lesson

Round 752,083 to the nearest hundred thousand.

800,000The 7 raises to an 8 and all of the other digits

turn to 0.800,000 is the

closest benchmark

number.

In this lesson you have learned how to round numbers to the

leading digit by using a number line.

Let’s ReviewGuided Practice

Round 24,972 to the nearest ten thousand.

Let’s ReviewExtension Activities

In your math journal, define what a benchmark number represents. Give examples.

Let’s ReviewExtension Activities

Draw a curved number line. Add the benchmark numbers and the midpoint for 49,621.

Round 49,621 to the nearest ten thousand.

Let’s ReviewQuick Quiz

Round 4,329 to the nearest thousand.

Let’s ReviewQuick Quiz

Round 564,789 to the nearest hundred thousand.