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### Number and algebra

### Geometry and measure

### Probability and statistics

### Working mathematically

### Advanced mathematics

### For younger learners

# 4 by 4 Mathdokus

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### Pebbles

### It Figures

### Bracelets

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Age 7 to 14

Challenge Level

- Problem
- Student Solutions
- Teachers' Resources

**An introduction to Mathdokus, and ways in which they might be used in the classroom, can be found in the Teachers' Resources for the 3 by 3 Mathdokus.**

For **Primary teachers** using this problem, you might also like your learners to work on Always, Sometimes or Never?, which appears in the same cell of the Primary curriculum mapping document.

You may also be interested in our other mathematical variations of Sudoku, which are suitable for Primary learners:

A First Product Sudoku

Intersection Sums Sudoku

Diagonal Sums Sudoku

For **Secondary teachers** using this problem, you might also like your students to work on Missing Multipliers, which appears in the same cell of the Secondary curriculum mapping document.

You may also be interested in our other mathematical variations of Sudoku:

Multiples Sudoku

Product Sudoku

LCM Sudoku

Difference Sudoku

*This problem featured in the NRICH Primary and Secondary webinar in October 2022.*

Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?

Suppose we allow ourselves to use three numbers less than 10 and multiply them together. How many different products can you find? How do you know you've got them all?

Investigate the different shaped bracelets you could make from 18 different spherical beads. How do they compare if you use 24 beads?