Printable · GCSE Foundation · ages 14-16

Rearranging formulae worksheet — GCSE Foundation

Fifteen questions on "rearranging formulae" — DfE statement A5. Print it, or print three versions so neighbours cannot copy by letter; the key gives the letter for each version.

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Rearranging formulae worksheet — GCSE Foundation

Maths · GCSE Foundation · A5 · Rearranging formulae · 15 questions

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1.Make a the subject of the formula b = 20 − a.
(a)a = 20 − b
(b)a = b − 20
(c)a = 20 + b
(d)a = −20 − b
2.Make x the subject of the formula y = x/2 − 5.
y = x
(a)x = (y + 5)/2
(b)x = 2y − 10
(c)x = 2y + 10
(d)x = 2y + 5
3.Make x the subject of the formula y = 3(x + 2).
(a)x = (y − 2)/3
(b)x = y/3 − 2
(c)x = 3y − 2
(d)x = y/3 + 2
4.A mobile phone tariff charges a fixed £15 plus 20p for every minute of calls made, so the total monthly charge, £C, for m minutes of calls is given by C = 15 + 0.2m. In a month where Ali's charge was £46.60, work out how many minutes of calls he made.
(a)233 minutes
(b)158 minutes
(c)308 minutes
(d)218 minutes
5.To rearrange y = 2x − 5 to make x the subject, Sam writes: 'Add 5 to both sides to get y + 5 = 2x, then divide both sides by 2 to get x = (y + 5)/2.' Which statement about Sam's method is correct?
y = 2x − 5
(a)Yes, but step 2 should give x = 2(y + 5)
(b)No; it should be x = (y − 5)/2
(c)Yes; x = (y + 5)/2 is right
(d)No; it should be x = y/2 + 5
6.To rearrange the formula y = 3x − 8 to make x the subject, Priya writes: 'Add 8 to both sides to get y + 8 = 3x, then divide both sides by 3 to get x = y + 8 ÷ 3.' Work out the correct expression for x.
y = 3x − 8
(a)x = 3(y + 8)
(b)x = (y − 8) / 3
(c)x = y + 8 / 3
(d)x = (y + 8) / 3
7.Make x the subject of the formula y = 5x + 3.
y = 5x + 3
(a)x = (y + 3)/5
(b)x = (y − 3)/5
(c)x = y/5 − 3
(d)x = 5(y − 3)
8.A rectangular sheep pen has perimeter P, length l and width w, connected by the formula P = 2l + 2w. A farmer has 60 m of fencing for the perimeter and sets the width at 8 m. Work out the length of the pen.
(a)30 m
(b)11 m
(c)22 m
(d)38 m
9.The formula for the area of a trapezium is A = (a + b)h / 2, where a and b are the parallel side lengths and h is the height. Make h the subject of the formula.
(a)h = 2A / a + b
(b)h = (a + b) / (2A)
(c)h = A / (a + b)
(d)h = 2A / (a + b)
10.The formula for the circumference of a circle is C = 2πr, where r is the radius. Make r the subject of the formula.
(a)r = C / (2π)
(b)r = C / π
(c)r = 2πC
(d)r = C − 2π
11.The perimeter of a rectangle is given by the formula P = 2(l + w), where l is the length and w is the width. A rectangular garden has a perimeter of 46 m and a length of 14 m. Rearrange the formula to make w the subject, then work out the width of the garden.
(a)9 m
(b)18 m
(c)37 m
(d)16 m
12.Make x the subject of the formula y = 4(x − 6).
(a)x = 4y + 96
(b)x = (y + 6)/4
(c)x = (y + 24)/4
(d)x = y/4 − 6
13.Make x the subject of the formula y = (x − 4)/5.
(a)x = 5(y + 4)
(b)x = 5y − 4
(c)x = y/5 + 4
(d)x = 5y + 4
14.Make m the subject of the formula w = m − 8.
(a)m = 8 − w
(b)m = w + 8
(c)m = w/8
(d)m = w − 8
15.The simple interest, £I, earned on a savings account is given by the formula I = PRT/100, where P is the amount invested in pounds, R is the interest rate per year and T is the time in years. Rearrange the formula to make P the subject.
(a)P = 100I / (RT)
(b)P = 100I/R
(c)P = 100RT/I
(d)P = IRT/100

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