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Sunday Times Teaser 3031 – End of the Beginning

by BRG on October 23, 2020

by Howard Williams

Published Sunday October 25 2020 (link)

Jenny is using her calculator, which accepts the input of numbers of up to ten digits in length, to prepare her lesson plan on large numbers. She can’t understand why the results being shown are smaller than she expected until she realizes that she has entered a number incorrectly.

She has entered the number with its first digit being incorrectly entered as its last digit. The number has been entered with its second digit first, its third digit second etc. and what should have been the first digit entered last. The number she actually entered into her calculator was 25/43rds of what it should have been.

What is the correct number?

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2 Comments Leave one →
  1. Brian Gladman permalink

  2. John Z permalink

    Excellent, Brian!

    BTW f can only equal 5 because we have

    b = 25/43 a or

    b / 25 = a / 43

    b is divisible by 25 therefore the last digit of b and the first digit of a is 5. (Zero is excluded because it can not be a first digit.)

    Here is my gas-guzzling, brute-force code. It spits out a solution after about 10 seconds:

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