Grade 3 Maths (IMO) : Division

Let’s talk about what division really is — it is repeated subtraction; much the way multiplication is repeated addition.

Let’s say I have the basic problem 16 ÷  4.  I could start with 16 and then subtract 4, subtract another 4, another 4, and another 4 until I run out and reach zero.  I would have to do this 4 times. If I had 16 cookies that I wanted to share equally among 4 friends, I could do the “one for you, one for you, one for you, and one for you” process and still end up with 4 cookies for each.

But what about 375 ÷ 50? If I don’t know how to divide by double digit numbers, the repeated subtraction process might actually be a good choice . . . at least showing some number sense to know that 375 divided by 50 means “How many 50’s in 375?” I know if I subtract 50 six times, I still have 75 left. I can subtract another 50 and I have 25 left over. So 375 ÷ 50 = 7 with a remainder of 25.

Dividing using the distributive law

Division Possible Split Calculation Answer
69 ÷ 3 60 + 9 (60 ÷ 3) = 20

(9 ÷ 3)  = 3

20 + 3 = 23
391 ÷ 3 390 + 1  (390 ÷ 3) = 130

(1 ÷ 3) = cannot be divided

130 with Remainder 1

 Long Division

Before a child is ready to learn long division, he/she has to know: Continue reading