Digit-Wise Subtraction Code

27. Digit-Wise Subtraction Code

In a secret code, every digit of a number is replaced independently according to a fixed rule. For example:

555555555 → 222222222

Using the same rule, what is the coded form of the number 89898989898?

Added 21 January 2012

Show Hint Show Solution

Hint:

Compare each corresponding digit in the example pair; what single arithmetic operation turns a 5 into a 2?

Solution:

The code subtracts 3 from each digit: 8 → 5 and 9 → 6. Applying this to every digit of 89898989898 gives 56565656565.

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