JEE Main 2017 · 8 Apr · Shift 1 · Mathematics Q86

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MathematicsSingle correct+4 / -1Question 86 of 90

Three persons P, Q and R independently try to hit a target. If the probabilities of their hitting the target are $\dfrac34$ , $\dfrac12$ and $\dfrac58$ respectively, then the probability that the target is hit by P or Q but not by R is :

\dfrac{21}{64}

\dfrac9{64}

\dfrac{15}{64}

\dfrac{39}{64}

Answer and worked solution

Official answer: A

$P(\text{P or Q})=1-\frac14\cdot\frac12=\frac78$ and $P(\text{not R})=\frac38$ , so the probability is $\frac{21}{64}$ .

Topics:Independent events

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JEE Main 2017 · 8 Apr · Shift 1, Mathematics question 86