StudentAidProbability & Statistics 1 — Variant 1
A Level Mathematics · 9709/51 · Oct/Nov 2021
Questions
4 of 7 questions shown here, checked against the paper. The others are in the PDF above — they contain diagrams or maths we could not yet verify, and we would rather show you the original than a transcription we are not sure of.
1
Two fair coins are thrown at the same time. The random variable is the number of throws of the two coins required to obtain two tails at the same time.
1(a)
[2]
Find the probability that two tails are obtained for the first time on the 7th throw.
1(b)
[2]
Find the probability that it takes more than 9 throws to obtain two tails for the first time.
2
A summary of 40 values of gives the following information: , , where is a constant.
2(a)
[2]
Given that the mean of these 40 values of is 34, find the value of .
2(b)
[2]
Find the variance of these 40 values of .
3
[5]
For her bedtime drink, Suki has either chocolate, tea or milk with probabilities 0.45, 0.35 and 0.2 respectively. When she has chocolate, the probability that she has a biscuit is 0.3. When she has tea, the probability that she has a biscuit is 0.6. When she has milk, she never has a biscuit. Find the probability that Suki has tea given that she does not have a biscuit.
4
A fair spinner has edges numbered . Another fair spinner has edges numbered . Each spinner is spun. The number on the edge on which a spinner comes to rest is noted. The random variable is the sum of the numbers for the two spinners.
4(a)
[3]
Draw up the probability distribution table for .
4(b)
[3]
Find .
Published by Cambridge Assessment International Education. Reproduced for study use.