**sum** of these 2 numbers?

The number theory questions in math competitions frequently focus on efficiency or numerical relationships. We have units on each of these categories in this course, and you don't need to work through all of the units in this course in order, you can jump directly to whichever one you want to practice.

The unit on Efficiency will provide you with a wide array of tools that will save you a lot of time and effort in math competitions, by shortening calculations or even skipping them entirely. It will also show you how to use relationships between numbers to work backwards and find unknowns. To learn more, you can either explore what's in this unit or read through the Number Theory: Efficiency Syllabus.

The unit on Factorization explores the relationships between numbers based on their factors. You will learn to use the prime factorization to find common divisors and multiples as well as ways to apply divisibility rules efficiently. To learn more, you can either explore what's in this unit or read through the Number Theory: Factorization Syllabus.