Topic Details (Notes format)

How to Calculate Modular Inverses

Subject: Mathematics

Book: Maths Mastery

A modular inverse of a number a (mod m) is x such that ax ≡ 1 (mod m). It exists only if gcd(a,m)=1. The Extended Euclidean Algorithm finds x for which ax + my=1, implying ax≡1 (mod m). For instance, to find the inverse of 3 modulo 7, we solve 3x + 7y=1, yielding x=5 because 3×5=15≡1 (mod 7). Modular inverses power encryption algorithms (RSA), solve congruences, and handle advanced computations in computer science. Mastery ensures you can manipulate modular arithmetic quickly for a wide range of cryptographic and number-theoretic tasks.

Practice Questions

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If a number is divisible by 9, it is also divisible by which of the following?

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The probability of rolling a sum of 7 with two dice is:

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What is the HCF of 48 and 180?

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What is the cube of 4?

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If a cone has a radius of 5 cm and a height of 12 cm, what is its slant height?

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The sum of the squares of two consecutive integers is 145. What are the integers?

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