1. Implementation
Review the mathematical concept.
Review the problem solving steps.
READ: Children read the part that is asking them to find something out.
UNDERSTAND: Children explain what they need to find out.
Children identify what information they will need to find it out.
Remove the coloured rectangle.
Children find the information they need to find it out.
CHOOSE A STRATEGY: Children identify strategies that they could use to find it out.
USE A STRATEGY: Children use a strategy to find it out.
Children record their thinking as they find it out.
CHECK: Children reread the part that asked them to find something out.
Children check that they have found it out.
Children check they have recorded their solution correctly.
Children follow the problem solving steps to solve the 2nd level of the problem, with minimal teacher guidance.
Children who solve the 2nd level, follow the problem solving steps to solve the 3rd level of the problem independently.
Children use the problems as a guide to create their own problem, either alone or in pairs/small groups.
Children solve their own problem.
Throughout the lesson, children share solution strategies.
At the end of the lesson, children explain how they created their own problems.

2. Lola collected 84 cans. Jill collected 90 cans.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Lola collected 84 cans. Jill collected 90 cans.
How many cans did Lola and Jill collect altogether?
Lola collected 78 cans. Jill collected 80 cans.
How many cans did Lola and Jill collect altogether?
Lola collected 40 cans. Jill collected 96 cans.
How many cans did Lola and Jill collect altogether?
Addition and Subtraction 15
Create your own problem! Now solve it!

3. Altogether Lola and Jill collected 117 cans. Jill collected 30 cans.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Altogether Lola and Jill collected 117 cans.
Jill collected 30 cans.
How many cans did Lola collect?
Altogether Lola and Jill collected 145 cans.
Jill collected 70 cans.
How many cans did Lola collect?
Altogether Lola and Jill collected 134 cans.
Jill collected 70 cans.
How many cans did Lola collect?
Addition and Subtraction 15
Create your own problem! Now solve it!

4. In a school choir there were 68 boys and 70 girls. How many children?
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
In a school choir there were 68 boys and 70 girls.
How many children?
In a school choir there were 68 boys and 60 girls.
How many children?
In a school choir there were 80 boys and 44 girls.
How many children?
Addition and Subtraction 15
Create your own problem! Now solve it!

5. Adela added a tens number and a two-digit number together and got 147.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Adela added a tens number and a two-digit number together and got 147.
What might the numbers be?
Adela added a tens number and a two-digit number together and got 165.
What might the numbers be?
Adela added a tens number and a two-digit number together and got 131.
What might the numbers be?
Addition and Subtraction 15
Create your own problem! Now solve it!

6. Matt thought of a number. He added 60. The answer was 114.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Matt thought of a number. He added 60.
The answer was 114.
What number did Matt first think of?
Matt thought of a number. He added 60.
The answer was 103.
What number did Matt first think of?
Matt thought of a number. He added 70.
The answer was 144.
What number did Matt first think of?
Addition and Subtraction 15
Create your own problem! Now solve it!

7. Jenny showed this number on her calculator. 85
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Jenny showed this number on her calculator. 85
She changed it so that it became this number
What did Jenny do to change 85 to 35?
Jenny showed this number on her calculator
She changed it so that it became this number
What did Jenny do to change 109 to 49?
Jenny showed this number on her calculator
She changed it so that it became this number. 90
What did Jenny do to change 175 to 90?
Addition and Subtraction 15
Create your own problem! Now solve it!

8. 90 + 47 has the same value as 47 + ____
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
has the same value as 47 + ____
has the same value as 57 + ____
has the same value as 80 + ____
Addition and Subtraction 15
Create your own problem! Now solve it!

9. Create your own problem! Now solve it!
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
April wrote this correct number sentence = 116.
Which of these number sentences is also correct?
= = = 46
April wrote this correct number sentence = 136.
Which of these number sentences is also correct?
= = = 46
April wrote this correct number sentence.
= 107.
Which of these number sentences is also correct?
= = = 107
Addition and Subtraction 15
Create your own problem! Now solve it!

10. In 60 years, Holly will be 104 years old. How old is Holly now?
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
In 60 years, Holly will be 104 years old.
How old is Holly now?
In 80 years, Holly will be 104 years old.
How old is Holly now?
In 40 years, Holly will be 87 years old.
How old is Holly now?
Addition and Subtraction 15
Create your own problem! Now solve it!

11. 30 years ago Holly was 43 years old. How old is Holly now?
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
30 years ago Holly was 43 years old.
How old is Holly now?
50 years ago Holly was 43 years old.
How old is Holly now?
30 years ago Holly was 17 years old.
How old is Holly now?
Addition and Subtraction 15
Create your own problem! Now solve it!

12. Create your own problem! Now solve it!
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Lydia recorded an addition number sentence using a tens number and a two-digit number that equalled 145.
What could the number sentences have been?
Lydia recorded an addition number sentence using a tens number and a two-digit number that equalled 105.
What could the number sentences have been?
Lydia recorded an addition number sentence using a tens number and a two-digit number that equalled 187.
What could the number sentences have been?
Addition and Subtraction 15
Create your own problem! Now solve it!

13. Create your own problem! Now solve it!
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Lydia recorded a subtraction number sentence using a tens number and a two-digit number that equalled 57.
What could the number sentences have been?
Lydia recorded a subtraction number sentence using a tens number and a two-digit number that equalled 17.
What could the number sentences have been?
Lydia recorded a subtraction number sentence using a tens number and a two-digit number that equalled 94.
What could the number sentences have been?
Addition and Subtraction 15
Create your own problem! Now solve it!

14. I have 70 more apples than oranges. I have 56 oranges.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
I have 70 more apples than oranges.
I have 56 oranges.
How many apples do I have?
I have 70 more apples than oranges.
I have 86 oranges.
How many apples do I have?
I have 68 more apples than oranges.
I have 40 oranges.
How many apples do I have?
Addition and Subtraction 15
Create your own problem! Now solve it!

15. Jenny showed this number on her calculator. 152
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Jenny showed this number on her calculator
She changed it so that it became this number
What did Jenny do to change 152 to 82?
Jenny showed this number on her calculator
She changed it so that it became this number
What did Jenny do to change 143 to 73?
Jenny showed this number on her calculator
She changed it so that it became this number
What did Jenny do to change 196 to 76?
Addition and Subtraction 15
Create your own problem! Now solve it!

16. Matt thought of a number. He subtracted 70. The answer was 58.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Matt thought of a number. He subtracted 70.
The answer was 58.
What number did Matt first think of?
Matt thought of a number. He subtracted 70.
The answer was 38.
What number did Matt first think of?
Matt thought of a number. He subtracted 60.
The answer was 28.
What number did Matt first think of?
Addition and Subtraction 15
Create your own problem! Now solve it!

17. I have 70 fewer apples than oranges. I have 124 oranges.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
I have 70 fewer apples than oranges.
I have 124 oranges.
How many apples do I have?
I have 90 fewer apples than oranges.
I have 124 oranges.
How many apples do I have?
I have 85 fewer apples than oranges.
I have 70 oranges.
How many apples do I have?
Addition and Subtraction 15
Create your own problem! Now solve it!

18. She kept 10 and gave the rest to Ben.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Betty had 39 shells.
She kept 10 and gave the rest to Ben.
How many shells did Betty give to Ben?
Betty had 79 shells.
She kept 30 and gave the rest to Ben.
How many shells did Betty give to Ben?
Betty had 64 shells.
She kept 20 and gave the rest to Ben.
How many shells did Betty give to Ben?
Addition and Subtraction 15
Create your own problem! Now solve it!

19. In this room there are 123 chairs. Mary came and took 70 chairs.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
In this room there are 123 chairs.
Mary came and took 70 chairs.
How many chairs are left?
In this room there are 113 chairs.
Mary came and took 40 chairs.
How many chairs are left?
In this room there are 194 chairs.
Mary came and took 110 chairs.
How many chairs are left?
Addition and Subtraction 15
Create your own problem! Now solve it!

20. Create your own problem! Now solve it!
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
In this room there are 82 chairs and next door there are 70 chairs.
There 132 children in the grade.
Are there enough chairs in the 2 rooms?
In this room there are 62 chairs and next door there are 40 chairs.
There 126 children in the grade.
Are there enough chairs in the 2 rooms?
In this room there are 78 chairs and next door there are 70 chairs.
There 132 children in the grade.
Are there enough chairs in the 2 rooms?
Addition and Subtraction 15
Create your own problem! Now solve it!

21. This room has 80 more chairs than next door.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
This room has 80 more chairs than next door.
How many chairs could be in each room?
This room has 40 more chairs than next door.
How many chairs could be in each room?
This room has 110 more chairs than next door.
How many chairs could be in each room?
Addition and Subtraction 15
Create your own problem! Now solve it!

22. How many spaces were empty?
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
A car park had 124 spaces.
90 cars were parked.
How many spaces were empty?
A car park had 167 spaces.
70 cars were parked.
How many spaces were empty?
A car park had 117 spaces.
40 cars were parked.
How many spaces were empty?
Addition and Subtraction 15
Create your own problem! Now solve it!

23. On which number did he place his counter?
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Stan placed a counter on a number on a hundred chart and moved iii and ended on 56.
On which number did he place his counter?
Stan placed a counter on a number on a hundred chart and moved iii and ended on 81.
On which number did he place his counter?
Stan placed a counter on a number on a hundred chart and moved iii and ended on 76.
On which number did he place his counter?
Addition and Subtraction 15
Create your own problem! Now solve it!

24. On which number did she place her counter?
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Lola placed a counter on a number on a hundred chart and moved hhh and ended on 56.
On which number did she place her counter?
Lola placed a counter on a number on a hundred chart and moved hhh and ended on 16.
On which number did she place her counter?
Lola placed a counter on a number on a hundred chart and moved hhh and ended on 31.
On which number did she place her counter?
Addition and Subtraction 15
Create your own problem! Now solve it!

25. Jenny thought of a number. She added 10. Her answer was 57.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Jenny thought of a number. She added 10.
Her answer was 57.
What number did Jenny think of?
Jenny thought of a number. She added 40.
Her answer was 57.
What number did Jenny think of?
Jenny thought of a number. She added 80.
Her answer was 127.
What number did Jenny think of?
Addition and Subtraction 15
Create your own problem! Now solve it!

26. Johnny thought of a number. He subtracted 10. His answer was 57.
Problem Solving
Add and subtract tens numbers to and from two-digit numbers,
counting forwards and backwards by 10s off the decade.
Johnny thought of a number.
He subtracted 10. His answer was 57.
What number did Johnny think of?
Johnny thought of a number.
He subtracted 40. His answer was 57.
What number did Johnny think of?
Johnny thought of a number.
He subtracted 90. His answer was 57.
What number did Johnny think of?
Addition and Subtraction 15
Create your own problem! Now solve it!