AMC 10 Daily Practice - Modular Arithmetic

Complete problem set with solutions and individual problem pages

Problem 1 Medium

Given that 7x\equiv 107\left( \text{mod}11 \right), the minimum value of \left| x \right| is            .

Answer:2

7x\equiv 107\left( \text{mod}11 \right),

7x\equiv 107-44\left( \text{mod}11 \right),

7x\equiv 63\left( \text{mod}11 \right),

x\equiv 9\left( \text{mod}11 \right),

x=-2, \left| x \right|=2.