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

If the average of five consecutive odd numbers is 25, what is the largest number?

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If the sum of three consecutive integers is 96, what are the integers?

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If the product of two numbers is 120 and their sum is 26, what are the numbers?

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

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What is the value of log₃(27)?

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If 8x = 512, what is the value of x?

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The sum of the reciprocals of two numbers is 1/4. If one number is 12, what is the other?

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What is the slope of a line passing through the points (2, 3) and (4, 7)?

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If x + y = 10 and xy = 21, what is the value of x³ + y³?

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What is the cube of 4?

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