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Fractional and negative indices

3 exam-style questions. Answers and the mark for each step are on the last page.

  1. Question 1Non-calculator · 6 marks

    Find the value of each expression. Do not use a calculator.

    (a) 251225^{\frac{1}{2}} (1)

    (b) 8−18^{-1} (1)

    (c) 272327^{\frac{2}{3}} (2)

    (d) (49)−12\left(\frac{4}{9}\right)^{-\frac{1}{2}} (2)

  2. Question 2Non-calculator · 5 marks

    Work with exact values and no calculator.

    (a) Work out 272/3×16−1/227^{2/3}\times16^{-1/2}. (3)

    (b) Solve 3x=1/273^x=1/27. (2)

  3. Question 3Non-calculator · 6 marks

    Show clear working. Do not use a calculator.

    (a) Solve 4x×2x+3=3224^x \times 2^{x + 3} = 32^2. You must show your working. (4)

    (b) 912×27n=3−49^{\frac{1}{2}} \times 27^n = 3^{-4}. Find the value of nn. You must show your working. (2)

Answers and marks

Question 1

(a) 55

  • B1 The correct answer, 55.

(b) 18\frac{1}{8}

  • B1 The correct answer, 18\frac{1}{8}.

(c) 99

  • M1 Finding 273=3\sqrt[3]{27} = 3.
  • A1 The correct answer, 99.

(d) 32\frac{3}{2}

  • M1 Flipping to 94\frac{9}{4} or square-rooting to 23\frac{2}{3}.
  • A1 The correct answer, 32\frac{3}{2}.

Question 2

(a) 94\frac{9}{4}

  • M1 Take the cube root before squaring.
  • M1 A negative half power is the reciprocal square root.
  • A1 Correct answer: 94\frac{9}{4}

(b) −3-3

  • M1 Write the reciprocal as a negative integer power.
  • A1 Correct answer: −3-3

Question 3

(a) x=73x = \frac{7}{3}

  • P1 Writing 4x4^x as 22x2^{2x}.
  • P1 Writing 32232^2 as 2102^{10}.
  • P1 Forming 3x+3=103x + 3 = 10.
  • A1 x=73x = \frac{7}{3}.

(b) n=−53n = -\frac{5}{3}

  • P1 Writing 912=319^{\frac{1}{2}} = 3^1 and 27n=33n27^n = 3^{3n}.
  • A1 n=−53n = -\frac{5}{3}.

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Fractional and negative indices

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Independent practice for Pearson Edexcel GCSE Mathematics (1MA1), not endorsed by Pearson.

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