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Statistics question

2002 · Shift 0 · Q63
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Statistics question

2002 · Shift 0 · Q63

JEE MainMathematicsStatisticsMCQ+4 / −1
In a class of 100 students there are 70 boys whose average marks in a subject are 75. If the average marks of the complete class is 72, then what is the average marks of the girls?
  1. A
    73
  2. B
    65
  3. C
    68
  4. D
    74
View written solutionFree

Correct answer: B

  1. Identify the given data
  • Total number of students =100= 100=100
  • Number of boys =70= 70=70
  • Therefore, number of girls =100−70=30= 100 - 70 = 30=100−70=30
  • Average marks of boys =75= 75=75
  • Average marks of whole class =72= 72=72
  1. Find total marks of the whole class

Total marks of class=100×72=7200\text{Total marks of class} = 100 \times 72 = 7200Total marks of class=100×72=7200

  1. Find total marks of the boys

Total marks of boys=70×75=5250\text{Total marks of boys} = 70 \times 75 = 5250Total marks of boys=70×75=5250

  1. Find total marks of the girls

Total marks of girls=7200−5250=1950\text{Total marks of girls} = 7200 - 5250 = 1950Total marks of girls=7200−5250=1950

  1. Find average marks of the girls

Average marks of girls=195030=65\text{Average marks of girls} = \frac{1950}{30} = 65Average marks of girls=301950​=65

  1. Check options
  • A: 737373
  • B: 656565
  • C: 686868
  • D: 747474

So the correct option is B.

Final Answer

65\boxed{65}65​

Previous

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