Clock Arithmetic and Number Theory - November 2003, Stage 3&4

Problems

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Clocked

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Is it possible to rearrange the numbers 1,2......12 around a clock face in such a way that every two numbers in adjacent positions differ by any of 3, 4 or 5 hours?

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Lastly - Well

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

What are the last two digits of 2^(2^2003)?

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What an Odd Fact(or)

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Can you show that 1^99 + 2^99 + 3^99 + 4^99 + 5^99 is divisible by 5?

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John's Train Is on Time

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

A train leaves on time. After it has gone 8 miles (at 33mph) the driver looks at his watch and sees that the hour hand is exactly over the minute hand. When did the train leave the station?

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Excel Investigation: the Difference of Two (same) Powers

Stage: 3 and 4 Challenge Level: Challenge Level:2 Challenge Level:2

If you take two integers and look at the difference between the square of each value, there is a nice relationship between the original numbers and that difference. Can you find the pattern using. . . .

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Transposition Fix

Stage: 4 Challenge Level: Challenge Level:1

Suppose an operator types a US Bank check code into a machine and transposes two adjacent digits will the machine pick up every error of this type? Does the same apply to ISBN numbers; will a machine. . . .

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Check Code Sensitivity

Stage: 4 Challenge Level: Challenge Level:1

You are given the method used for assigning certain check codes and you have to find out if an error in a single digit can be identified.

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Check Codes

Stage: 4 Challenge Level: Challenge Level:1

Details are given of how check codes are constructed (using modulus arithmetic for passports, bank accounts, credit cards, ISBN book numbers, and so on. A list of codes is given and you have to check. . . .

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Composite Notions

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.