Tuesday, 7 April 2015

modular arithmetic - What is 51 in mathbbZ11?

I am trying to understand what this question is asking and how to solve it. I spent some time looking around the net and it seems like there are many different ways to solve this, but I'm still left confused.




What is the multiplicative inverse of 5 in Z11.

Perform a trial and error search using a calculator to obtain your answer.




I found an example here:




In Z11, the multiplicative inverse of 7 is 8 since 7 * 8 \equiv 56 \pmod {11}.




This example is confusing to me because 1 \pmod {11} \equiv 1. I don't see how 56 is congruent to 1 \pmod {11}.

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