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Build numbers with a chosen digit sum

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Number Play · Explore digit sums · 3:26

You'll learn: Use constraints to compare possible numbers

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Build numbers with a chosen digit sum

3:26

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Build numbers with a chosen digit sum

You'll learn: Use constraints to compare possible numbers

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Same topic

Explore digit sums

2

A number and its digit sum are different
3:33
A number and its digit sum are different
You'll learn: Separate place value from adding digits
Count appearances of a digit
3:32
Count appearances of a digit
You'll learn: Count occurrences rather than just numbers containing the digit

Next topic

Recognise and construct palindromes

2

Numbers that read the same both ways
3:29
Numbers that read the same both ways
You'll learn: Recognise and build palindromes
Reverse add and test again
3:35
Reverse add and test again
You'll learn: Follow a repeated number transformation accurately

Next topic

Explore the Kaprekar routine

2

Rearrange subtract and repeat
3:35
Rearrange subtract and repeat
You'll learn: Follow the four-digit routine with valid starting digits
Different starts can meet the same result
3:48
Different starts can meet the same result
You'll learn: Compare selected trajectories and recognise a fixed result

Next topic

Find number patterns in clocks and calendars

1

Clock and calendar digit puzzles
3:30
Clock and calendar digit puzzles
You'll learn: Find patterns within the chosen display convention

Next topic

Use mental arithmetic and spot patterns

3

Regroup to make a friendly calculation
3:34
Regroup to make a friendly calculation
You'll learn: Explain mental addition and multiplication
An operation changes more than the digits
3:38
An operation changes more than the digits
You'll learn: Reason about possible result sizes
Always sometimes or never
3:40
Always sometimes or never
You'll learn: Support a claim or find a counterexample

Next topic

Explore the Collatz process

2

Two rules create a number journey
3:28
Two rules create a number journey
You'll learn: Apply half for even numbers and three times plus one for odd numbers
Examples leave a bigger question
3:42
Examples leave a bigger question
You'll learn: Understand what an unproved conjecture means

Next topic

Estimate quantities sensibly

2

Estimate using a small count
3:37
Estimate using a small count
You'll learn: Use representative groups to estimate a larger quantity
Choose a sensible scale for an estimate
3:33
Choose a sensible scale for an estimate
You'll learn: Check whether a result is plausible

Next topic

Explore games and winning strategies

1

Work backwards in a counting game
3:32
Work backwards in a counting game
You'll learn: Find useful target totals for adding one two or three