my math world

Monday, 26 November 2012

Division as repeated Subtraction (2)


Multiplication is repeated addition, and it is like jumps on the number line.  

5 × 4 =  20.   Five jumps of 4 gets you to 20.
Division is repeated subtraction.  You make jumps of four backwards from 20 till you hit 0: 

20 ÷ 4 = 5.    20 − 4 − 4 − 4 − 4 − 4 = 0
Five jumps of 4 gets you from 20 till 0.

 What division is illustrated here?


2.  Draw jumps backwards to illustrate the division sentences.


30 ÷ 5 = 


28 ÷ 4 = 


42 ÷ 6 = 



4.  Solve using repeated subtraction OR adding up to the number being divided.
40 ÷ 20 = __
90 ÷ 30 = __
30 ÷ 15 = __
52 ÷ 13 = __
34 ÷ 17 = __
69 ÷ 23 = __
45 ÷ 15 = __
90 ÷ 15 = __
90 ÷ 18 = __

5.  If  12 × 2 = 24, then 13 × 2 is __   How about division?  Use the previous problem to help you solve the next one.
a.
24 ÷ 2 = __
26 ÷ 2 = __
28 ÷ 2 = __
30 ÷ 2 = __
d.
60 ÷ 2 = __
66 ÷ 2 = __
70 ÷ 2 = __
78 ÷ 2 = __


6.  Try the same kind of thing when dividing by 3.
a.
30 ÷ 3 = __
36 ÷ 3 = __
39 ÷ 3 = __
d.
81 ÷ 3 = __
90 ÷ 3 = __
99 ÷ 3 = __

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