Adding  Friendly  Numbers  Con3nued   1.  Clear off the hundreds board. Write the

equation: 17+20. Ask students to demonstrate how they would solve this problem. Note that when we added 2 tens to 17, the 7 did not change.

2.  Check the answer using bundles sticks of tens and ones.

3.  Give students a range of problems using ‘friendly numbers’. Encourage students to do a mental calculation, and then check their answer using the hundreds board or a calculator.

Ac3vity  Process                      Subtrac3ng  Friendly  Numbers  1.  Give each student a 1-100 hundreds board. 2.  Ask them to place a counter on the number 83. 3.  Ask students to take 10 away from 83 and place

another counter on the answer. Write the equation on a whiteboard.

4.  Leave the counter on 83 and take away 20. Write the equation on a whiteboard. Continue taking away 30 through to 80. Write the equations Compare the equations and discuss the pattern.

   

 Australian  Curriculum  Year  Two  ACMNA030  Solve  simple  addi-on  and  subtrac-on  problems  using  a  range  of  efficient  mental  and  wri8en  strategies  Proficiency Strand: Understanding – connecting number calculations with counting sequences; combining numbers flexibly; identifying and describing the relationship between addition and subtraction. Reasoning – using known facts to derive strategies for unfamiliar calculations                Ac3vity  Process-­‐Adding  Friendly  Numbers  1.  Give  each  student  a  1-­‐100  hundreds  board.  2.  Ask  them  to  place  a  counter  on  the  number  7.  3.  Ask  students  to  add  10  to  7  and  place  another    

counter  on  the  answer.  Write  the  equa-on  on  a  whiteboard.  

4.  Leave  the  counter  on  7  and  add    20.    Write  the  equa-on  on  a  whiteboard.    Con-nue  adding  30  through  to  90  to  7.  Write  the  equa-ons.  Compare  the  equa-ons  and  discuss  the  pa8ern.  Also  discuss  the  turn-­‐arounds.  

       

Introduc3on  Students  will    revise  addi-on  and  subtrac-on  strategies  of  coun-ng  on,  combina-ons  to  ten,  doubles,  near  doubles,  add  ten  and  bridge  through  ten  .  Students  will  add  the  friendly  numbers  strategy  to  their  range  of  strategies.    Resources  •  Early  FISH  Kit  •  Hundreds  board  •  Transparent  counters  •  Mini-­‐  whiteboard  and  washable  pens  •  Bundle  s-cks  •  Calculator    •  Addi-on  and  Subtrac-on  strategy  prac-ce  cards  •  Who  has?  More  or  less    •  Number  fact  wheel  •  Number  line  1-­‐100  

Time/Classroom  Organisa3on  Revise  known  strategies  and  apply  to  a  range  of  addi-on  and  subtrac-on  problems.  Allow  20  minutes  to  introduce  the  near  doubles  strategy,  and  give  students  opportuni-es  to  prac-ce  regularly.                

 Word  Wall:  hundreds,  add,  adding,  addi-on,  combina-ons  to  ten,  doubles,  bridge  to  ten,  equa-on,  turn  arounds,  solve,  take  away 2.2.4

7+10=17 7+20=27 7+30=37 7+40=47 7+50=57 7+60=67 7+70=77

20 + 17 = 37

10+23= 20+27 = 70+12=

48+10= 61+20= 27+30=

Subtrac3ng  Friendly  Numbers  Con3nued                 1.  Clear off the hundreds board. Write the equation:

46-20. Ask students to demonstrate how they would solve this problem. Note that when we subtracted 2 tens from 46, the 6 did not change.

2.  Check the answer using bundles sticks of tens and ones.

3.  Give students a range of subtraction problems using ‘friendly numbers’. Encourage students to do a mental calculation, and then check their answer using the hundreds board or a calculator.

     Varia3ons  &  Extensions  1.  Number line addition

Resources: Number line 1-100 Repeat the above activity process. Use an unmarked number line to add ‘friendly numbers’. Have students draw a number line and place a number, for example: 38. Add 10 more. What number would you be on? Add 20 more. Scaffold the discussion: do we need to count in ones? Is there a quicker way to add each ten?  

Contexts  for  Learning  Play: Whole class addition to 25 game: This game can be played as a small group game. Each player takes 5 cards each. Investigation: Give students a number, for example 46. Give students 2 minutes and ask them to write as many questions as they can which have that number as the answer. Source: First Steps in Number – Understand Operations. 2010. Rigby: Port Melbourne. p136. Real life experience: Using junk mail, have students choose and circle three prices to add and write the three amounts on their own whiteboard. When finished share the strategies they have used to add the amounts. Routines and Transitions: Use the whole class addition to 25 cards as a transition. Have the Fact Wheels available for students to use when they have finished other activities.  Assessment  The number wheel activity could be used as an assessment item to determine if students can add and subtract ‘friendly numbers’. Achievement Standard: perform simple addition and subtraction calculations using a range of strategies. Background  Reading  The development of any standard algorithms should follow the development of mental and informal written approaches and be introduced as an extension of students’ existing strategies to enable them to deal with larger numbers easily . It is now understood that introducing standard written algorithms for simple numbers can be counter-productive.  

Resources: Who has? More or less Give each student a card. The first student calls out the question on the card. The student with the answer calls out, and then continues with the next question. The game continues until all the cards have been called. 3.  Number Wheel

Resources: Number fact wheel Give each student a number fact wheel. Ask students to write the addition or subtraction operation you want to practice in the centre of the wheel, and numbers around the inner circle. Students apply the operation and write in the answers using washable pen. Digital  Resources  http://www.ideal-resources.com.au/index.php      

83-10=73 83-20=63 83-30=53 83-40=43 83-50=33 83-60=23

48-10= 62-20= 27-20=

I have 70 Who has 10 less?

I have 50 Who has 20 more?

I have 55 Who has 5 less?

+20 20

22 14

9

16

80

For  example,  emphasising  addi-on  of  two-­‐digit  numbers  in  a  standard  column  format  where  no  trading  is  required  actually  encourages  students  to  focus  on  each  column  separately  and  to  lose  sight  of  the  significance  of  the  places.  This  can  lead  to  many  of  the  errors  they  later  make  when  trading  is  needed. Source:  First  Steps  in  Number  –  Understand  Opera-ons.  2010.  Rigby:  Port  Melbourne.  p144.          Year  three  NAPLAN  Numeracy  test  links  Addi-on  and  Subtrac-on  –  number  problems  Addi-on  and  Subtrac-on  –  word  problems    Links  to  Related  MAGs  2.1.4  –  Func-on  Machine  2.1.5  –  Addi-on  and  Subtrac-on  1  2.3.2  –  Number  sequences  3.1.5  –  Addi-on  Strategies  –  1      Suppor3ng  Mathema3cal  Vocabulary  Development    Providing  a  range  of  quality  mathema-cal  texts  and  text  types  that  link  to  and  extend  the  pupils’  interests.      Crea-ng  interac-ve  working  walls/displays  so  that  pupils  can  capture  vocabulary  for  later  use.      

Adapted for use in the Cairns Diocese with the permission of the Catholic Education Office Toowoomba