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O-LevelMathematicsProbability4024/21 · May/June 2024 · Q119 Marks

On any day in January, the probability the temperature at a weather station is above 14°C is 0.35 . There are 31 days in January. Find the number of days in January when you would expect the temperature to be above 14°C.

  1. (a)(i)On any day in January, the probability the temperature at a weather station is above 14°C is 0.35 . There are 31 days in January. Find the number of days in January when you would expect the temperature to be above 14°C.[1]
  2. (a)(ii)(a)The temperature on two consecutive days in January is recorded. Complete the tree diagram.[2]
  3. (a)(ii)(b)Find the probability that the temperature is above 14°C on both days.[1]
  4. (a)(ii)(c)Find the probability that the temperature is above 14°C on only one of the two days.[2]
  5. (b)In a group of 14 children: • 8 wear red T-shirts • 1 wears a green T-shirt • 5 wear blue T-shirts. Two children are chosen from the group at random. Find the probability that they wear different coloured T-shirts.[3]

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Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

  1. [1] 10 or 11
  2. [2] Correct tree diagram
  3. [2] M1 for 2 or 3 probabilities completed correctly
  4. [2] 0.65, 0.65, 0.35, 0.65 oe
  5. [1] 0.1225 oe e.g. 49/400
  6. [2] 0.455 oe e.g. 91/200
  7. [2] M1 for [2x]0.35×0.65
  8. [3] 106/182 oe e.g. 53/91
  9. [3] M2 for 1 - ( (8/14)*(7/13) + (1/14)*(0/13) + (5/14)*(4/13) ) oe
  10. [3] or (8/14)*(6/13) + (1/14)*(13/13) + (5/14)*(9/13) oe
  11. [3] or M1 for (8/14)*(7/13) + (1/14)*(0/13) + (5/14)*(4/13) oe or 3 correct products
  12. [3] After 0 scored, SC1 for 106/196 e.g. 53/98 oe

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About this question

Topic
Probability, O-Level Mathematics (syllabus 4024). Structured question, 9 marks.
Source
O-Level Mathematics, May/June 2024 Paper 2 Variant 1, question 11.

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