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Question: Answered & Verified by Expert
An urn contains 9 balls of which 3 are red, 4 are blue and 2 are green. Three balls are drawn at random from the urn. The probability that the three balls have difference colours is
MathematicsThree Dimensional GeometryMHT CETMHT CET 2021 (21 Sep Shift 2)
Options:
  • A $\frac{1}{14}$
  • B $\frac{3}{14}$
  • C $\frac{1}{7}$
  • D $\frac{2}{7}$
Solution:
1403 Upvotes Verified Answer
The correct answer is: $\frac{2}{7}$
$\begin{aligned} \text { Required probability } & =\frac{{ }^3 \mathrm{C}_1 \times{ }^4 \mathrm{C}_1 \times{ }^2 \mathrm{C}_1}{{ }^9 \mathrm{C}_3} \\ & =\frac{3 \times 4 \times 2}{\left(\frac{9 !}{3 ! 6 !}\right)}=\frac{24 \times 6}{9 \times 8 \times 7}=\frac{2}{7}\end{aligned}$

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