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A box contains $20$ fuses of which $5$ are defective. If $2$ fuses are chosen together at random, what is the probability that both the fuses are defective?

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closed as not constructive by Andres Caicedo, Paul, Julian Kuelshammer, Hurkyl, Michael Greinecker May 8 '13 at 8:06

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What is the number of ways of selecting 2 objects out of 5? Out of 20? –  Milind May 8 '13 at 4:04
Please do not just pose a problem with no background information and what you have tried yourself. Such questions do not fit for MSE. –  Michael Greinecker May 8 '13 at 11:40

1 Answer 1

Number of ways of getting both the fuses as defective = $5C_2$

Number of ways of selecting any two fuses = $20C_2$

Hence, Probability = $\dfrac{5C_2}{20C_2}$ = $\dfrac{1}{19}$

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