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APMOPS 2011 Question 14

APMOPS · APMOPS 2011

Question 14

$P_n$ is defined as the product of the digits in the whole number $n$. For example, $P_{19}=1\times9=9$, $P_{32}=3\times2=6$. Find $P_{10}+P_{11}+\cdots+P_{98}+P_{99}$.