Absolute value equations and inequalities, in context

Grade 11 Math Worksheet

Circle the best answer.

1. 1.

   Esme needs road marks x whose distance from mile 1 is less than twice their distance from mile 7: |x − 1| < 2|x − 7|. Which x work?

   • 5 < x < 13
   • x < 5, on the side nearer mile 1
   • x < 4, the side nearer mile 1 than mile 7
   • x < 5 or x > 13
2. 2.

   Jun rewrites g(x) = |x − 1| + |x − 4| without bars, as a piecewise function. Which version is right?

   • 5 − 2x for x < 1, and 2x − 5 for x ≥ 1
   • 2x − 5 for x < 1, 3 for 1 ≤ x ≤ 4, and 5 − 2x for x > 4
   • 5 − 2x for x < 1, −3 for 1 ≤ x ≤ 4, and 2x − 5 for x > 4
   • 5 − 2x for x < 1, 3 for 1 ≤ x ≤ 4, and 2x − 5 for x > 4
3. 3.

   A rod's length L (mm) must meet |L − 50| ≤ 0.4. Its mass is 0.4L grams and must meet |0.4L − 20.2| ≤ 0.2. Which lengths does Kira accept?

   • 49.6 ≤ L ≤ 51
   • 50.3 ≤ L ≤ 50.4
   • 50 ≤ L ≤ 50.4
   • 49.6 ≤ L ≤ 50.4
4. 4.

   A kitchen scale reads within 2% of the true mass m: |R − m| ≤ 0.02m. It reads R = 49 g. Which true masses does Luz find possible?

   • m ≤ 48.04 or m ≥ 50
   • About 48.02 ≤ m ≤ 49.98
   • About 48.04 ≤ m ≤ 50
   • m ≥ 48.04
5. 5.

   A thermostat set to s keeps the room within 1.5° of s. The room must stay from 18° to 24°. Which settings s does Milo allow?

   • 19.5 ≤ s ≤ 22.5, or |s − 21| ≤ 1.5
   • 18 ≤ s ≤ 24
   • 18.75 ≤ s ≤ 23.25
   • 16.5 ≤ s ≤ 25.5, or |s − 21| ≤ 4.5
6. 6.

   Depots sit at miles 3 and 11. Noah serves spots x nearer depot 3 than depot 11, |x − 3| < |x − 11|, and within 5 miles of it. Which x qualify?

   • −2 ≤ x < 7
   • 7 < x ≤ 8
   • x < 7
   • −2 ≤ x ≤ 7
7. 7.

   Pia graphs y = |x² − 4| and slides a flat line y = k up and down. For which k does |x² − 4| = k have exactly four solutions?

   • 0 < k ≤ 4
   • k > 0
   • k > 4
   • 0 < k < 4
8. 8.

   A sensor reads every spot within 2 m of its position h: |x − h| ≤ 2. Ren needs it to read both x = 5 and x = 8. Which positions h work?

   • 6 ≤ h ≤ 7
   • 3 ≤ h ≤ 7
   • 6 < h < 7
   • 3 ≤ h ≤ 10
9. 9.

   Tala solves |x² − 4| = 3x by splitting it into two branches and checking each answer. Which solution set is right?

   • x = −1 and x = 4
   • x = 1 and x = 4 only
   • x = −4, −1, 1 and 4
   • x = 4 only: the second branch has no real roots

10. Read this first

    Line 1

    x − 1 = 2x + 3, so x = −4. Line 2: x − 1 = −2x + 3, so x = 4/3. Line 3: the solutions are −4 and 4/3.

11. 10.

    Zee checks a worked solution of |x − 1| = |2x + 3|. Which correction is right?

    • No line is wrong: both answers check in the equation
    • Line 2: it should be −x − 1 = 2x + 3, giving x = −4/3
    • Line 2: −(2x + 3) is −2x − 3, which gives x = −2/3
    • Line 3: drop 4/3, since it fails the check, and keep −4