Primary Four: Rearranging the Digits to Form the Largest/Smallest Number.

In the Primary Four Mathematics Syllabus (2007), students need to understand the number notations and place values of (ten thousands, thousands, hundreds, tens and ones.) Based on this requirement, there are many questions that came out from it to test students on this point.

One questions is to ask students to re-arrange five digits to get either the largest/smallest number. The solution process to teach your children would be,

1) Ask the student to arrange the digits from largest to smallest or smallest to largest depending on the question asked.
2) Check for the digit "0" (zero) if the question is requesting for Smallest Number. Otherwise, students can just put down the 5-digits number in the order they have arranged in Step 1.
3) If there is the digit "0", ask students to read the instructions again to check if it is asking the student to form the largest 5-digit number.
4) If there is such instruction to form the smallest 5-digits number, student need to move the digit "0" from the first digit to the second digit (eg. From 0,1,2,7,8 to 1,0,2,7,8). Otherwise just put down the digit in the order arrange ignoring the digit zero. (i.e. 1278)
5) After the re-arrangement in Step 4, students can just write the digits in the order they have arranged to answer the question.

With the ongoing need to add critical thinking into questions, I have now seen questions where they have added in restrictions in forming the largest number. For example,

"Rearrange the digits 7,1,3,4,9 to form the largest digits that is more less than 50 000."

The solution process is as follows:

1) Rearrange the digits from biggest to the smallest, from left to right. (i.e. 9,7,4,3,1)
2) Looking from the biggest digit to the smallest, take out the digit that is smaller than the first digit of the restriction. (ie. The first digit of the restriction is 5 thus we choose the digit 4).
3) After taking out the digit from Step 2, strike it away from the list. (i.e 9,7,3,1).
4) Write the rest of the digits in the same order onto the right hand side of the digit selected from Step 2 and you should get the answer. (ie 49731).

In conclusion, the digit "0" would complicate questions that ask for the smallest number and restrictions posed could complicate questions that ask for the largest number. So parents please ask children to pay attention to these two aspect when answering questions that need to rearrange digits.