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Question: Answered & Verified by Expert
Three numbers are chosen at random from 1 to 20 . The probability that they are consecutive is
MathematicsProbabilityWBJEEWBJEE 2009
Options:
  • A $\frac{1}{190}$
  • B $\frac{1}{120}$
  • C $\frac{3}{190}$
  • D $\frac{5}{190}$
Solution:
2377 Upvotes Verified Answer
The correct answer is: $\frac{3}{190}$
Hints: Total number of cases ; ${ }^{20} \mathrm{C}_3=\frac{20 \times 19 \times 18}{2 \times 3}=20 \times 19 \times 3=1140$
Total number of favourable cases $=18$
$\therefore$ Required probability $=\frac{18}{1140}=\frac{3}{190}$

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