Hundredth decimal digit of a huge power of 1 plus root 2
Question
Consider the number . Find the digit sitting in the 100th place after its decimal point.
Short answer
. The sum is an integer, since the odd powers of cancel in the binomial expansions. As , the original number equals an integer minus a tiny positive amount, so its first several hundred decimal digits are all .
Adapted from Zhou, A Practical Guide to Quantitative Finance Interviews, sec. 4.2 Combinatorial Analysis, '100th digit', p.70; question and answer rewritten by SelfMadeQuant.com.
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