Number bases

There are 25 NRICH Mathematical resources connected to Number bases
More Secret Transmissions
problem

More Secret Transmissions

Age
16 to 18
Challenge level
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In 'Secret Transmissions', Agent X could send four-digit codes error free. Can you devise an error-correcting system for codes with more than four digits?
Secret Transmissions
problem

Secret Transmissions

Age
14 to 16
Challenge level
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How can Agent X transmit data on a faulty line and be sure that her message will get through?
Oh for the mathematics of yesteryear
problem
Favourite

Oh for the mathematics of yesteryear

Age
11 to 14
Challenge level
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A garrison of 600 men has just enough bread ... but, with the news that the enemy was planning an attack... How many ounces of bread a day must each man in the garrison be allowed, to hold out 45 days against the siege of the enemy?
Back to the Planet of Vuvv
problem

Back to the Planet of Vuvv

Age
11 to 14
Challenge level
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There are two forms of counting on Vuvv - Zios count in base 3 and Zepts count in base 7. One day four of these creatures, two Zios and two Zepts, sat on the summit of a hill to count the legs of the creatures they could see. The creature looking to the West wrote 122. The creature looking to the East wrote 22. The creature looking to the South wrote 101. The creature looking to the North wrote 41. In which direction are the 2 Zios looking and in which directions are the 2 Zepts looking?
Phew I'm Factored
problem

Phew I'm Factored

Age
14 to 16
Challenge level
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Explore the factors of the numbers which are written as 10101 in different number bases. Prove that the numbers 10201, 11011 and 10101 are composite in any base.
Composite Notions
problem

Composite Notions

Age
14 to 16
Challenge level
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A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.
Knapsack
problem

Knapsack

Age
14 to 16
Challenge level
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You have worked out a secret code with a friend. Every letter in the alphabet can be represented by a binary value.
Guesswork
problem
Favourite

Guesswork

Age
14 to 16
Challenge level
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Ask a friend to choose a number between 1 and 63. By identifying which of the six cards contains the number they are thinking of it is easy to tell them what the number is.
Alien Counting
problem

Alien Counting

Age
7 to 11
Challenge level
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Investigate the different ways these aliens count in this challenge. You could start by thinking about how each of them would write our number 7.
Balance Power
problem

Balance Power

Age
11 to 18
Challenge level
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Using balancing scales what is the least number of weights needed to weigh all integer masses from 1 to 1000? Placing some of the weights in the same pan as the object how many are needed?

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