Arithmetic Grade Five

Lesson Forty-two: Count-bys

We normally count by ones, but we can count by any amount we want to count by. Here are three examples: 


Counting by 100s:  100, 200, 300, 400, 500, 600 ...
Counting by 20s:   20, 40, 60, 80, 100, 120, 140, 160 ...
Counting by 5s:	   5, 10, 15, 20, 25, 30, 35, 40 ...
Knowing your count-bys will help you with your basic multiplication facts. Here are a few more examples: 

Counting by 7s:  7, 14, 21, 28, 35, 49, 56, 63 ...
Counting by 8s:  8, 16, 24, 32, 40, 48, 56, 64 ...
Counting by 9s:	 9, 18, 27, 36, 45, 54, 63, 72 ...
Remember that you can make a count-by list using either addition or multiplication: 

COUNTING BY FOURS:

	ADDITION	MULTIPLICATION		NEXT NUMBER
	4		   4 x 1		  4
	4+4		   4 x 2		  8
	4+4+4		   4 x 3		 12
	4+4+4+4		   4 x 4		 16
	4+4+4+4+4	   4 x 5		 20
	4+4+4+4+4+4	   4 x 6		 24

Continue to next page of lesson