AMC 10 Step by Step
Log inSign up
Printable

2018 AMC 10A Problem 19

Include the solutionBack to the problem
2018 AMC 10A Problem 19AMC 10 Step by Step
Name:                             Date: September 13, 2026
Modular Arithmetic · difficulty 3 of 5 · about 4 min · position P16-20

A number mm is randomly selected from the set {11,13,15,17,19}\{11,13,15,17,19\} , and a number nn is randomly selected from {1999,2000,2001,…,2018}\{1999,2000,2001,\ldots,2018\} . What is the probability that mnm^n has a units digit of 11 ?

  1. A)

    15\frac{1}{5}

  2. B)

    14\frac{1}{4}

  3. C)

    310\frac{3}{10}

  4. D)

    720\frac{7}{20}

  5. E)

    25\frac{2}{5}

Working