Differentiation practice problems A level Maths, Topic 5
Differentiating powers, ex and ln x, the chain, product and quotient rules, tangents, stationary points and connected rates of change. Try each question before you look: use the hint if you are stuck, then reveal the worked solution one step at a time.
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Key equations for differentiation
| d/dx(xn) = nxn−1 | power rule |
|---|---|
| d/dx(ekx) = kekx, d/dx(ln x) = 1/x | exponentials and logs |
| dy/dx = dy/du × du/dx | chain rule |
| d/dx(uv) = u′v + uv′ | product rule |
A formula booklet is provided in the exam. Answers within 2.5% are marked correct, and you can type fractions such as 1/6. What the booklet gives you, and what it leaves out, is in our A level Maths formula booklet guide.
Warm-up questions
Quick checks on the core ideas. If these feel easy, go straight to the exam-style questions.
Hint
Differentiate, then substitute.
Worked solution
- d/dx(4x3) = 12x2.
- At x = 2: 12 × 4 = 48.
Hint
dy/dx = 2x − 3.
Worked solution
- dy/dx = 2(5) − 3 = 7.
Hint
Use the chain rule with u = 3x.
Worked solution
- d/dx(e3x) = 3e3x: B.
Exam-style questions
Questions at the level of the A level Maths exam. The ones marked Challenge combine more than one idea.
Hint
Set dy/dx = 0.
Worked solution
- dy/dx = 2x − 6 = 0.
- x = 3.
Hint
Chain rule: 4(2x + 1)3 × 2.
Worked solution
- dy/dx = 8(2x + 1)3.
- At x = 0: 8.
Hint
Product rule with u = x and v = ex.
Worked solution
- dy/dx = ex + xex.
- At x = 1: 2e = 5.44.
Hint
d/dx(ln x) = 1/x.
Worked solution
- dy/dx = 1/4 = 0.25.
Hint
dA/dt = dA/dr × dr/dt, with A = πr2.
Worked solution
- dA/dr = 2πr = 10π at r = 5.
- dr/dt = 10/(10π) = 1/π = 0.318 cm/s.
Exam question practice
One original exam-style question in the style of an A level paper. Answer it in full, with working, before you open the mark scheme: M marks are for method, A marks for accurate answers that follow from it, and B marks for correct statements on their own.
Exam-style question style · 9 points · about 9 minutes
An open box is made from a 12 cm by 12 cm square of card by cutting a square of side x cm from each corner and folding up the sides.
- (a) Show that the volume is V = x(12 − 2x)2.
- (b) Find the value of x that gives the maximum volume.
- (c) Find the maximum volume and show that it is a maximum.
- (d) Explain why x must be less than 6.
Write your full answer on paper first, then open the scoring guide and tick each point you earned.
Scoring guide and model answer
Part (a)
The base is (12 − 2x) by (12 − 2x) and the height is x.
Part (b)
V = 144x − 48x2 + 4x3. dV/dx = 144 − 96x + 12x2 = 12(x − 2)(x − 6) = 0. x = 6 gives no box, so x = 2.
Part (c)
V = 2 × 82 = 128 cm3. d2V/dx2 = 24x − 96 = −48 < 0 at x = 2, so it is a maximum.
Part (d)
The side 12 − 2x must be positive.
Your mark: 0 of 9
Common mistakes in differentiation
- Forgetting to multiply by the inner derivative in the chain rule.
- Using the product rule as (uv)′ = u′v′.
- Not justifying the nature of a stationary point.
- Mixing up which rate is given and which is wanted in connected rates of change.
Keep going
Revise the ideas behind these questions:
Then try real exam questions: A level Maths past papers, with official scoring guidelines. · All A level Maths units