The last few days we have been practising short division both with and without remainders. This has been a learning experience for EVERYONE because some of us had never seen or done short division before and others of us had done some in the past but could not recall the exact steps to complete them.
Mrs Baldwin asked us the question
Which of these numbers are divisible by… 2 … 5 … 10
Mathematicians have developed divisibility tests for many numbers and you can use these to identify numbers, or create numbers, divisible by whatever you want.
We were each given the Divisibility test and then practiced using these tests to create some numbers.
Create a 5-digit number divisible by 3 – with no repeat digits
Create a 6 digit number divisible by 4.
Create a 5 digit number divisible by both 2 and 3
Each time we thought we discovered one we would test it by doing short division, that way we were practising this skill as well! We knew it passed the test because there would be no remainders.
Our next challenge was to place 3 digits into the boxes (no repeats) so that:
- the first digit is divisible by 1, and
- the first 2-digit number is divisible by 2, and
- the whole 3-digit number is divisible by 3
We were told that there were 115 possible solutions to this problem. So as a class we started recording our results on the board.
At the end of the lesson we found at least 85 possible solutions. We then talked about how good mathematicians are never convinced that all the solutions have been found unless they have a logical proof. We then used the strategy of drawing a tree diagram to help us find all possible solutions. Our class worked in groups and we each were given a number to use for the first digit to draw our tree diagrams. Here are our solutions!
We then compared these with our first round of solutions. Although there were a few we needed to fix up and change, we think for our first time recording and collating our data using the strategy of a tree diagram, we did a pretty good job!
As an extra challenge Mrs Baldwin gave us the following task:
There is a 10 digit number that passes all divisibility tests when. You need to use all the numbers from 0-9 with no repeats. There is only one solution. You need to prove your answer by showing evidence that your number passes all divisibility tests.
We have yet to have anyone in class solve this challenge! It has been wonderful to see some students really try to solve this problem and work together as a team to attempt to do this.