UniGeniusGCSE Maths · Edexcel 1MA1

Worksheets · Foundation and Higher

Formulae and changing the subject

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

  1. Question 1Non-calculator · 2 marks

    The time, TT minutes, to roast a chicken of mass ww kg is given by T=40w+20T = 40w + 20.

    (a) Work out the roasting time for a chicken of mass 2.52.5 kg. Give your answer in hours and minutes. (2)

  2. Question 2Non-calculator · 4 marks

    Change the subject of each formula.

    (a) v2=u2+2asv^2 = u^2 + 2as. Make ss the subject. (2)

    (b) A=πr2A = \pi r^2, where r>0r > 0. Make rr the subject. (2)

  3. Question 3Calculator · 3 marks

    (a) y = (3x23x^{2} −- 2)/(x2x^{2} + 4), where x > 0. Make x the subject and state the complete range of possible values of y. (3)

Answers and marks

Question 1

(a) 2 hours

  • M1 Working out 40×2.5+20=12040 \times 2.5 + 20 = 120.
  • A1 2 hours (120 minutes).

Question 2

(a) s=v2−u22as = \dfrac{v^2 - u^2}{2a}

  • M1 Subtracting u2u^2: v2−u2=2asv^2 - u^2 = 2as.
  • A1 s=v2−u22as = \frac{v^2 - u^2}{2a}.

(b) r=Aπr = \sqrt{\dfrac{A}{\pi}}

  • M1 Writing r2=Aπr^2 = \frac{A}{\pi}.
  • A1 r=Aπr = \sqrt{\frac{A}{\pi}}.

Question 3

(a) x = \sqrt{}((4y + 2)/(3 - y)), with −1/2 < y < 3.

  • P1 Establishing (3−y)x2=4y+2(3-y)x^{2}=4y+2 or an equivalent valid method.
  • P1 Establishing 3−14/(x2+4)3-14/(x^{2}+4) or an equivalent valid method.
  • A1 Correct answer: x = \sqrt{}((4y + 2)/(3 - y)), with −1/2 < y < 3.

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Formulae and changing the subject

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