Math CentralQuandaries & Queries


Question from Saranya:


The question is to find the numbers from sum and difference.
The Sum = 14 and the difference = 2

I found in this web site some useful answers. but my kid is going second grade only. She don't know how to do a division or multiplication.
So can you please explain on how to find the answer using only the Addition and Subtraction.

Thanks in advance.

Hi Saranya,

I can suggest two approaches to solve this problem. The first is very visual.

First approach:

Find 14 objects. Marbles, jelly beans, pencils anything. Put them in a pile. Now separate the objects into two piles. Count the number of items in each pile. The sum of these numbers is 14. What is the difference between the two numbers? Can you arrange the objects into two piles so that the difference of the numbers in the two piles is 2?

Second approach:

What number, added to itself gives 14? In other words what is half of 14? Now you have two numbers, actually two copies of the same number, with a sum of 14 but their difference is zero. Increase one of the numbers by one and now the sum is 15. If you decrease the other number by one the sum of the two numbers is now 14. What is their difference?

I hope this helps,

About Math Central
* Registered trade mark of Imperial Oil Limited. Used under license.


Math Central is supported by the University of Regina and the Imperial Oil Foundation.
Quandaries & Queries page Home page University of Regina Imperial Oil Foundation