A-LevelMathematicsProbability and statistics9709/61 · Oct/Nov 2025 · Q610 Marks
The masses, in kilograms, of large and small bags of potatoes have the independent distributions N(2.5, 0.05) and N(0.8, 0.02) respectively.
- (a)Find the probability that the total mass of a randomly chosen large bag of potatoes and a randomly chosen small bag of potatoes is more than 3.55 kg.[5]
- (b)Find the probability that the mass of a randomly chosen large bag of potatoes is less than 3 times the mass of a randomly chosen small bag of potatoes.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.
- B1B1 SOI B1 for N(3.3, ...) B1 for 0.07 give at early stage OE.
- M1 For standardising with their values.
- M1 For area consistent with their values.
- A1
- B1 Give at early stage. OE.
- M1 Give at early stage.
- M1 For standardising with their values. Must have used the vars for denom.
- M1 For area consistent with their values.
- A1
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