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  • Question
  • A bag contains 5 blue and 4 black balls. Three balls are drawn at random. What is the probability that 2 are blue and 1 is black?


  • Options
  • A. 1/3
  • B. 2/5
  • C. 1/6
  • D. None of these

  • Correct Answer
  • 1/6 

    Explanation

    Let S be the sample space and E be the event of drawing 3 balls out of which 2 are blue and 1 is back .

    Then, n (S)= Number of ways of drawing 3 balls out of 9=9c3
    = (9 x 8 x 7) / (3 x 2 x 1)
    = 84 and

    n(E) = Number of ways of drawing 2 balls out of 5 and 1 ball out of 4 .
    = 5C2 4C11
    = (5 x 4) / (2 x 1) + 4 = 14

    ? P(E) = n(E)/n(S) = 14/84 = 1/6


  • More questions

    • 1. 
      0.0169 / 0.013=?

    • Options
    • A. .13
    • B. .013
    • C. 1.3
    • D. 13
    • Discuss
    • 2. 
      Two posts are x meter apart and the height of one is double that of the other. If from the midpoint of the line joining their feet, an observer finds the angular elevations of their tops to be complementary, then the height (in meter) of the shorter post is :

    • Options
    • A. x 2 ?2
    • B. x 4
    • C. x ?2
    • D. x ?2
    • Discuss
    • 3. 
      If p/q =4/5, then the value of 4/7 + {(2q - p) / (2q + p)} is?

    • Options
    • A. 3 / 7
    • B. 34
    • C. 1
    • D. 2
    • Discuss
    • 4. 
      What is 25% of 25% is equal to?

    • Options
    • A. 6.25
    • B. .625
    • C. .0625
    • D. .000625
    • Discuss
    • 5. 
      The number .05 is hoe many percent of 20?

    • Options
    • A. 25
    • B. .025
    • C. .25
    • D. 2.5
    • Discuss
    • 6. Find the lowest common multiple of 24, 36 and 40.

    • Options
    • A. 120
    • B. 240
    • C. 360
    • D. 480
    • Discuss
    • 7. 
      8 1/ 3% expressed as a fraction is?

    • Options
    • A. 25/3
    • B. 3/25
    • C. 1/12
    • D. 1/4
    • Discuss
    • 8. 
      .025 in terms of term of rate per cent is?

    • Options
    • A. .25%
    • B. 2.5%
    • C. 0.25%
    • D. 371/2%
    • Discuss
    • 9. 
      What percentage of 2/7 is 1/35?

    • Options
    • A. 2.5%
    • B. 10%
    • C. 25%
    • D. 20%
    • Discuss
    • 10. 
      A sum of ? 4000 is lent out in two parts, one at 8% simple interest and other at 10% simple interest. If the annual interest is ? 352, the sum lent at 8% is

    • Options
    • A. ? 1600
    • B. ? 2400
    • C. ? 1800
    • D. ? 2800
    • Discuss


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