This is the second in a series of blog posts about how to systematically teach problem-solving skills using I See Problem-Solving, outworking the EEF research (recommendation 3) about using rich problems to learn mathematics.

When children have a really secure understanding of place value, I love using sum of the digit challenges. Here’s the task we’re coming to later:

The build-up focuses on the meaning of the sum of the digits. We start by ordering 74, 312, 214 & 47, and identifying how many digits in each number. Then we work out the sum of the digits for each, noting that the largest number, 312, had the smallest digit sum. To consolidate this skill, we have a go at this:

We also find numbers where the sum of the digits is 8. Example numbers that the children come up with include 53, 44000, 123500 and we even get an infinity sign for repeated zeros! Next, a quick recap on finding multiples:

After this, we are into the main task (number with sum of digits of 13, multiple of 4). Discussions were held about where to start: listing the multiples of 4, or finding all the 2-digit numbers with a sum of the digits of 13? The key question, it was decided was ‘which narrows down the possible answers more?’ Once the answer was found (76) it’s onto the explain and extend tasks:

 

We also made the point that, for the example above, we don’t need to cross out those beautiful workings out!

I’m trying to make problem-solving accessible for all children, whilst ensuring that every child is challenged. I hope you find I See Problem-Solving super-helpful. The LKS2 and KS1 versions are in production!

Also in this series:
Equals Means Same As Task
Number Sequences and Negative Numbers

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2 thoughts on “Learning to Problem-Solve: sum of the digits

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