Discia GCSE Maths › Number › Surds

Surds worksheet

10 GCSE practice questions with answers, free to print. Every sheet is generated, so you can make a fresh one whenever you need it.

10 questions 46 marks Sheet 1
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  1. 4 marks
    (a)

    Write \(\sqrt{ 54 }\) in the form \(a\sqrt{b}\), where \(a\) and \(b\) are integers and \(b\) is as small as possible.

    (b)

    Simplify \(4\sqrt{ 32 }\)

    Give your answer in the form \(a\sqrt{b}\), where \(b\) is as small as possible.

  2. 2 marks

    \(\sqrt{n} = 7\sqrt{ 5 }\)

    Calculate the value of \(n\).

  3. 6 marks
    (a)

    Write \(\sqrt{ 27 } + \sqrt{ 12 }\) in the form \(a\sqrt{b}\), where \(b\) is as small as possible.

    (b)

    Write \(\sqrt{ 396 } - \sqrt{ 99 }\) in the form \(a\sqrt{b}\), where \(b\) is as small as possible.

  4. 7 marks
    (a)

    Multiply out the brackets and simplify \(\sqrt{ 13 }\left(\sqrt{ 13 } + 5\right)\)

    (b)

    Multiply out the brackets and simplify \(\left(3 + \sqrt{ 7 }\right)\left(2 - \sqrt{ 7 }\right)\)

    (c)

    Multiply out the brackets and simplify \(\left(6 + \sqrt{ 6 }\right)\left(6 - \sqrt{ 6 }\right)\)

  5. 4 marks
    (a)

    Rationalise the denominator of \(\frac{ 20 }{\sqrt{ 5 } }\)

    Give your answer in its simplest form.

    (b)

    Rationalise the denominator of \(\frac{ 9 }{\sqrt{ 5 } }\)

  6. 6 marks
    (a)

    Rationalise the denominator and simplify \(\frac{ 39 }{ 4 + \sqrt{ 3 } }\)

    Give your answer in the form \(p - q\sqrt{ 3 }\), where \(p\) and \(q\) are integers.

    (b)

    Rationalise the denominator and simplify \(\frac{ 34 }{ 6 - \sqrt{ 2 } }\)

    Give your answer in the form \(p + q\sqrt{ 2 }\), where \(p\) and \(q\) are integers.

  7. 5 marks
    (a)

    Write \(\sqrt{ 20 } + \sqrt{ 5 }\) as a single surd \(\sqrt{c}\), where \(c\) is an integer.

    (b)

    Explain why \(\sqrt{ 3 } + \sqrt{ 5 }\) cannot be written as a single surd in the same way.

  8. 6 marks

    A rectangle has width \(\sqrt{ 90 }\) cm and length \(\sqrt{ 160 }\) cm.

    (a)

    Calculate the area of the rectangle.

    (b)

    Calculate the perimeter of the rectangle.

    Give your answer in the form \(a\sqrt{b}\) cm, where \(b\) is as small as possible.

  9. 4 marks
    (a)

    Simplify \(\sqrt{ 147 }\) fully.

    Give your answer in the form \(a\sqrt{b}\), where \(a\) and \(b\) are integers and \(b\) is as small as possible.

    (b)

    Write \(4\sqrt{ 275 }\) in the form \(a\sqrt{b}\), where \(b\) is as small as possible.

  10. 2 marks

    \(\sqrt{n} = 3\sqrt{ 7 }\)

    Find the value of \(n\).

Answers

  1. (a) \(3\sqrt{ 6 }\)
    (b) \(16\sqrt{ 2 }\)
  2. \(245\)
  3. (a) \(5\sqrt{ 3 }\)
    (b) \(3\sqrt{ 11 }\)
  4. (a) \(13 + 5\sqrt{ 13 }\)
    (b) \(-1 -\sqrt{ 7 }\)
    (c) \(30\)
  5. (a) \(4\sqrt{ 5 }\)
    (b) \(\frac{ 9\sqrt{ 5 } }{ 5 }\)
  6. (a) \(12 - 3\sqrt{ 3 }\)
    (b) \(6 + \sqrt{ 2 }\)
  7. (a) \(\sqrt{ 45 }\)
    (b) \(\sqrt{ 3 }\) and \(\sqrt{ 5 }\) are not multiples of the same surd, so there is nothing to collect. In particular \(\sqrt{ 3 } + \sqrt{ 5 }\) is not \(\sqrt{ 8 }\): square roots do not add like that, since \(\sqrt{9} + \sqrt{16} = 3 + 4 = 7\) while \(\sqrt{9 + 16} = \sqrt{25} = 5\).
  8. (a) \(120\ \text{cm}^2\)
    (b) \(14\sqrt{ 10 }\ \text{cm}\)
  9. (a) \(7\sqrt{ 3 }\)
    (b) \(20\sqrt{ 11 }\)
  10. \(63\)

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