We can use rectangular bars instead of unit cubes.
Look at how we can represent the numbers 9 and 6 using
rectangular bars.
9
6
We can compare the two rectangular bars like this:
9
6
3
Think! Which model below is the correct way to represent
the numbers 3 and 5? Why?
5
Note s
3
5
2
3
2
Common Errors
Remind the child that the bars must always be aligned to the left so that the difference between the bars
is read accurately.
58
Visible Thinking in Mathematics 2A (2nd Edition)
(M)VTM_2A_c03.indd 58
© 2014 Marshall Cavendish International (Singapore) Private Limited
6/6/13 10:15 AM
Look at these problems.
Problem 1
Daniel has 60 cards. John has 24 cards.
How many cards do they have altogether?
Problem 2
Daniel has 60 cards. John has 24 more cards than Daniel.
How many cards do they have altogether?
Problem 3
Daniel has 60 cards. John has 24 fewer cards than Daniel.
How many cards do they have altogether?
Think! How are they similar? How are they different? Underline the key
words that make them different from one another. Can you use
the same model to solve these problems?
Match.
60
Daniel
John
24
60
Daniel
John
Daniel
60
John
60
Note s
24
?
•
•
Problem 1
?
•
•
Problem 2
•
•
Problem 3
24
?
Teaching Tips
The key words are ‘more than’ and ‘fewer than’. The person who has more will have a longer rectangular bar.
Conversely, the person who has less will have a shorter bar.
60
Visible Thinking in Mathematics 2A (2nd Edition)
(M)VTM_2A_c03.indd 60
© 2014 Marshall Cavendish International (Singapore) Private Limited
6/6/13 10:15 AM
More Model Drawing
Thinking Platform
Look at the problem below.
Problem 1
Farah has 2 more bookmarks than Chester. If they have
8 bookmarks altogether, how many bookmarks does Farah have?
Think! Which solution below is correct?
Solution A
Solution B
2 + 8 = 10
5 + 5 = 10
5+2=7
8–2=6
3 + 3 =6
3+2=5
Farah has 7 bookmarks.
Farah has 5 bookmarks.
Note s
Draw a model for the correct solution.
Teaching Tips
This problem involves a comparison of two unknown numbers — the number of bookmarks Farah and Chester
each have. Using a model, the child will be able to see pictorially how the total of 8 bookmarks is distributed
between the two and how the 2 bookmarks are part of the total.
© 2014 Marshall Cavendish International (Singapore) Private Limited
(M)VTM_2A_c03.indd 65
Visible Thinking in Mathematics 2A (2nd Edition)
65
6/6/13 10:15 AM
Think Out Of The Box!
1. Janet had 80 more stickers than Wilson. How many stickers must
Janet give to Wilson so that Wilson will have 16 more stickers than
Janet in the end?
2. At a party, there were 82 more adults than children and 28 more
boys than girls. If there were 506 people altogether, how many
girls were there at the party?
3.
Aaron had $24 more than Teck Lim. After Aaron gave $40 to Teck
Lim, Teck Lim had twice as much as Aaron. How much money did
Aaron have at first?
Note s
Link
For more reading and practice, you may also refer to chapter 3 of My Pals Are Here Maths 2A (3rd Edition).
82
Visible Thinking in Mathematics 2A (2nd Edition)
(M)VTM_2A_c03.indd 82
© 2014 Marshall Cavendish International (Singapore) Private Limited
6/6/13 10:15 AM