Working memory and mental arithmetic

Mental arithmetic demands two things at once: remembering the numbers and doing something with them. Children with weaker working memory lose the numbers.

What it looks like

A child calculates 47 + 28 correctly when written down, but says "I forgot the first number" when asked orally. Or reaches the end of a long division and cannot remember the remainder.

What helps

• Write it down. Removing the memory load leaves the maths visible.
• Chunk it. Short steps, written, rather than one long chain.
• Use visuals. Bar models and number lines act as external memory.
• Reduce speed pressure. Working memory drops sharply under time stress.

The important message

Weak working memory is not weak intelligence. With the load removed, the reasoning is often excellent — which is exactly what we see in one-to-one sessions.