How many
$10$ digit natural numbers do not contain the digit $6?$ Numbers cannot start with zero.
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How many values can the first digit take?
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For each of those values, how many different numbers that do not contain the digit
$6?$ -
Think of the different values each of the remaining digit can take.
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The first digit can be 8 different options
$($i.e. not$0$and$6)$and the rest can be anything but$6.$The number of numbers without any 6s is$8 \times 9^9.$(Note: We don’t expect you to calculate the final value!)