Magic Number Division

We have been learning a division strategy in class this past week. I have decided to put the steps on the blog incase students need help at home completing homework or studying for the test (there hasn't been a date set yet for a test).

With "Magic Number" division, students use the magic numbers 10, 5, 2 and 1 and their multiples to solve more complicated division questions. The idea is to take the divisor (so if the question is 96 divided by 5, the divisor is 5) and be able to multiply it by each magic number. Always start with the biggest magic number (10). Once you have multiplied the divisor by 10, see if that number can be taken away from the dividend (96). In this case, 50 CAN be taken away from 96. Write the magic number you used along the side and take away the 50 from the dividend.

Next, see if you can use the 10 again (in this case no, because we will have 46 remaining). So move on to the next magic number (5). Multiply the divisor (5) by 5 and see if you can subtract it from the new total. If you can, write the magic number on the side again and subtract the answer. (5X5=25, so you can take this away from 46). You will have 21 remaining.

Then, see if you can use 5 again (ALWAYS make sure you can't use the same number before moving on to the next). If you can't, move onto the next magic number (2). Multiply the divisor by 2 (5x2=10) and take away the answer from your total (21-10=11) and write the magic number along the side.

Again, check to see if you can use the magic number again. In this case we can, because 10 can be taken away from 11. So write the magic number along the side and take away the answer again (11-10=1).

Move on to the next magic number. Multiply the divisor by the 1. If it can be taken away from the total, subtract until the final total is SMALLER than the divisor.

Once you are left with a total that is smaller than your divisor or zero, add up the magic numbers and put the total at the top. That is your answer. Anything left at the bottom is the REMAINDER.

This may sound confusing and be a lot of steps but many students do find this way of dividing simple and easy. It only has them focusing on multiples of 10, 5, 2 and 1 which many students have memorized (or should have memorized at this point in the year). In grade 5 they move from this strategy to "Divide, Multiply, Subtract, Bring-Down" strategy that many of us used in school.

I have attached photos with instructions that will hopefully help make this as clear as possible. I'm happy to show parents in person as well if you ever want to stop by after school some time! :)