**How many grains of sand are there on a beach? Could you count them? How long would it take?**

We can work this out by making some estimates. By lining up some and against a ruler, I counted 25 grains in 1cm. From this, I can conclude that:

a square of side 1cm would hold around 252 = 625 grains of sand.

a cube of side 1cm would hold around 253 = 15,625 grains of sand.

a cubic metre (100cm x 100cm x 100cm) would hold around 15,625,000,000 grains of sand. Thatâ€™s more than 15 billion grains! And thatâ€™s just in one cubic metre!

A small beach with an area of 50,000 square metres, whose sand was 1m deep, would have a volume of 50,000 cubic metres. This would therefore contain 781,250,000,000,000 grains of sand. Thatâ€™s more than 781 trillion grains!

**How long would it take to count the sand?**

Assuming you can count 1 grain per second, the table shows how many grains would be counted after different time periods.

If you spent your whole life counting sand, you would only count 16% of a cubic metre! Youâ€™d need another 6 people to count with you for their whole lives to complete this task. To count the whole beach, youâ€™d need more than 300,000 people counting sand for their whole lives!

So although itâ€™s an interesting idea to ponder, a little Maths shows you that counting sand will take you a long, long time. Estimating is a much better idea!

**Counting sand at 1 grain per second**

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