Math 1A Singapore-Counting and Comparing-Chapter 6.1

math 1a sg, counting and comparing, chapter 6.1, make a ten and count, make a ten and count from 10. greater and smaller,

Counting and Comparing


Look at the eggs and count all the eggs.

....

....
..

Count all the eggs: 1,2,3,4,5,6,7,8,9,10,11,12,13.

....
....
10 eggs
..
3 eggs

Count on from 10: 11,12,13.

So, 13 is 10 and 3.

As like as,

11 is 10 and 1.

12 is 10 and 2.
14 is 10 and 4.
15 is 10 and 5.
16 is 10 and 6.
17 is 10 and 7.
18 is 10 and 8.
19 is 10 and 9.
20 is 10 and 10.


1. Make a ten and count.


(a)

...

...
...
...

Solution:

Make a ten and count from 10.

....

....
..
..

Count from 10: 11,12,12,14,15,16.

So, There are 16 butterflies.

16 is 10 and 6.


(b)

.....

.....
..

Solution:

Make a ten and count extra bananas.

....

.... 10

..

. 5

10 and 5 make 15.

15 is 10 and 5.

So, there are 15 bananas.


(c)

.......

.......
.

Solution:

Make a ten and count others.

....

....  10

...

... 8

10 and 8 make 18

18 is 10 and 8.

So, there are 18 frogs.


2. (a) How many balls are there?

.....

...
....


(b) 10 and 5 make .


(c) 10 + 5 = .

Solution:

(a)

Make 10 and count the extra balls.

.....

... 10

.... 5

10 and 5 make 15

15 is 10 and 5.

So, there are 15 balls.

(b) 10 and 5 make 15.

(c) 10 + 5 = 15.


3. (a) How many stamps are there?

.........

...


(b) 10 and 4 make  


(c) 10 + 4 = .

Solution:

(a)

Make a ten and count the extra stamps.

.........10

...4

10 and 4 make 14.

So, there are 14 stamps.

(b) 10 and 4 make 14.

(c) 10 + 4 = 14.


4. Complete the addition sentences.


(a)

.........

....

10 + 5 =


(b) 

.........

.......

10 + =

Solution:

(a) 10 + 5 = 15.

(b) 10 + 8 = 18.


5. Count from 1 to 20. Then count backwards.

Solution:

Count from 1 to 20:

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20.

Count backwards:

20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1.


6. What are the missing numbers?

(a)
 
17
18
19
 
 
(b)
9
 
 
12
13
 
(c)
16
 
 
13
 
 
(d)
2
4
6
 
10
12
 
(e)
17
15
13
 
 
 
5

Solution:

(a)
16.
17.
18.
19.
20.
 
(b)
9.
10.
11.
12.
13.
 
(c)
16.
15.
14.
13.
12.
 
(d)
2.
4.
6.
8.
10.
12.
14.
(e)
17.
15.
13.
11.
9.
7.
5.


7. Which set has the greater number?

A
B
.
..

..
..
.

Answer: B


8. Which set has the smaller number?

A
B
.
.

..
..
.

Answer: A


9. Which set has the greatest number?

    Which set has the smallest number?

A
B
.
.
.

.
.
.
.
.

C
D
.

.


.
.
.

Solution:

Count the pineapples of each set. And we get:


A
B
6
10
C
D
5
7

 So, Set B has the greatest number and set C has the smallest number?


10. (a) Which is greater, 14 or 17?

      (b) Which is smaller, 19 or 12?

Solution:

(a)

.●.●.●.●.●.●.●.●.● 10

.●.●.● 4
----------------------------------
         Total = 14

.●.●.●.●.●.●.●.●.● 10

.●.●.●.●.●.● 7
----------------------------------
                      Total = 17

14 = 10 + 4

17 = 10 + 7

7 > 4

So, 17 is greater than 14.

(b)

.●.●.●.●.●.●.●.●.● 10

.●.●.●.●.●.●.●.● 9
----------------------------------
           Total = 19

.●.●.●.●.●.●.●.●.● 10

.● 2
----------------------------------
                    Total = 12

19 = 10 + 9

12 = 10 + 2

2 < 9

So, 12 is smaller than 19.


11. Compare these numbers:

12
16
20
8

(a) Which number is greatest?

(b) Which number is the smallest?

(c) Arrange the numbers in order. Begin with the smallest.

Solution:

(a) 20 is the greatest number.

(b) 8 is the greatest number.

(c) Arranged numbers as below:


8
12
16
20
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