How many Linear combinations of random variables questions are there for 9709?

This page collects 9 recent Cambridge Mathematics (9709) past-paper questions tagged to Linear combinations of random variables. Each links straight to instant marking against the official 9709 scheme.

How are Linear combinations of random variables answers marked?

Type or photograph your working and MarkScheme scores it against the real 9709 mark scheme for this topic — method, accuracy and any band descriptors — so you see exactly where the marks are.

Where can I learn Linear combinations of random variables first?

Start with the free Mathematics lesson on Linear combinations of random variables, then come back and drill past-paper questions under timed conditions.

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9709 · topic questions

Linear combinations of random variables

Mathematics9 questions

9 past-paper questions on Linear combinations of random variables

9709/61 · May/June 20256 marks
The random variable S is the sum of 100 independent values of W and 200 independent values of X. (ii) Use a suitable…
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9709/62 · October/November 20246 marks
Use approximating distributions to find the probability that the total number of lemon sweets in the 10 bags is less than the…
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9709/61 · May/June 20245 marks
The random variable X has the distribution N(31.2, 10.4²). Two independent random values of X, denoted by X₁ and X₂, are chosen.…
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9709/61 · October/November 20245 marks
The masses, in kilograms, of small and large bags of wheat have the independent distributions N(16.0,0.4) and N(51.0,0.9)…
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9709/62 · May/June 20245 marks
Find P(X₁ > 2X₂ −3).
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9709/62 · May/June 20255 marks
The times, in minutes, taken by students to complete a test are normally distributed with mean 125 and variance 50. Two students…
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9709/61 · October/November 20243 marks
Find the probability that during a randomly chosen 5-minute period the total number of customers arriving at both desks is less…
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9709/61 · May/June 20253 marks
At an entertainment centre, the cost for using a particular video game is $0.40 per minute. The number of minutes for which…
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9709/61 · May/June 20253 marks
Each day, 35 people independently use the video game. (b) Find the mean and variance of the total amount paid by 35 people.
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Question stems are shortened previews. Open a question to attempt the full version and have it marked.

Worked example

What a lost mark actually looks like

This answer reaches the right coordinates and still drops a mark — the conclusion is stated, but never justified. Examiners pay for the reasoning, not the answer.

MARKED

80%

Strong

M1dy/dx = 3x^2 - 12x + 9M1 earned
M1(x - 1) $(x - 3) = 0$ M1 earned
A1 $x = 1$ or $x = 3$ A1 earned
B1(1, 5) is a maximum and (3, 1) is a minimumB1 not earned

B1 — withheld
You stated the nature of each point correctly, but stated it without justification. This mark needs the reasoning shown — either evaluate the second derivative (d²y/dx² = 6x − 12, giving −6 at $x = 1$ and +6 at $x = 3$ ) or show a sign change of dy/dx either side of each point. An unsupported assertion earns nothing here even when the conclusion is right.

Linear combinations of random variables (9709) past-paper questions — marked instantly

These are real Cambridge Mathematics past-paper questions on Linear combinations of random variables. Open one, attempt it, then upload your working — MarkScheme grades it against the official 9709 mark scheme so you see exactly where the marks are won and lost on this topic.

Mark your answer →Learn Linear combinations of random variables 9709 grade boundaries

Frequently asked questions

How many Linear combinations of random variables questions are there for 9709?: This page collects 9 recent Cambridge Mathematics (9709) past-paper questions tagged to Linear combinations of random variables. Each links straight to instant marking against the official 9709 scheme.
How are Linear combinations of random variables answers marked?: Type or photograph your working and MarkScheme scores it against the real 9709 mark scheme for this topic — method, accuracy and any band descriptors — so you see exactly where the marks are.
Where can I learn Linear combinations of random variables first?: Start with the free Mathematics lesson on Linear combinations of random variables, then come back and drill past-paper questions under timed conditions.