Groups of Ten and Where Numbers Sit on a Line

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What this lesson covers

  • Each digit is worth its place: 4 in 47 is worth 40.
  • Ten tens make one hundred.
  • Numbers from 101 to 120 start with "one hundred and".
  • Groups of ten make big collections quick to count.
Key idea

What each digit is worth

  • In 47, the 4 is in the tens place, so it is worth 40.
  • The 7 is in the ones place, so it is worth 7.
  • In 115, each 1 is worth something different.
NumberDigitWorth
47440
4777
115first 1100
115second 110
11555
Key idea

Ten tens make a hundred

  • Bundle iceblock sticks in tens: 10, 20, 30, up to 100.
  • Ten bundles of ten is 100 sticks. One hundred is ten tens.
  • One more bundle makes 110, which is 11 tens.
Bundles of tenSticks
990
10100
11110
12120
Key idea

Maths blocks

Worked example

Saying numbers past 100

  • Say "one hundred and", then the rest of the number.
NumberSay it
101one hundred and one
110one hundred and ten
113one hundred and thirteen
120one hundred and twenty
Worked example

Count a big pile in tens

  • Here are some pāua shells. Make piles of ten.
  • 7 piles and 4 left over: count 10, 20, 30, 40, 50, 60, 70, then 71, 72, 73, 74.
  • There are 74 shells. Tens first, then ones.
Piles of tenLeft overTotal
7474
9696
112112
120120
Worked example

Find a spot on the number line

  • This line is marked 0, 10, 20, up to 120.
  • 61 is just 1 past 60, so it sits just after 60.
  • 85 is halfway between 80 and 90.
NumberBetweenSits
6160 and 70just after 60
8580 and 90halfway
117110 and 120close to 120
Key idea

Try it: hop along in ones and tens

Common mistakes

  • In 38, the 3 is worth 3.
    The 3 is in the tens place, so it is worth 30.
  • Count a big pile one shell at a time.
    Make groups of ten first. Count the tens, then add the ones left over.
  • 61 goes halfway between 60 and 70.
    61 is only 1 more than 60, so it goes just after 60.

Your turn

1

What is the 9 worth in 93?

2

How many tens make 100?

3

There are 8 piles of ten shells and 3 more shells. How many shells?

4

On a line marked in tens, 58 sits between which two numbers?

5

Write 114 in words.

Show answer

1. 90 2. 10 3. 83 4. 50 and 60, close to 60 5. one hundred and fourteen

Summary

What to take away

  • A digit is worth its place.
  • Ten tens make one hundred.
  • Group in tens, then count the tens and the ones.
  • Use the tens marks to find where a number sits.
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More in Number

Numbers to 120: Read, Write and CompareNotesGroups of Ten and Where Numbers Sit on a LineNotesRounding, Skip Counting, Odd and EvenNotesAdding and Taking Away: Facts to 20 and TensNotesStory Problems: Adding and Taking Away to 100NotesTimes and Share: 2s, 5s and 10sNotesHalves, Thirds and QuartersNotesComparing Fractions and Finding the WholeNotesNZ Coins and Notes: Count and Make MoneyNotes

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