Question
Assertion $(A) :$ The probability that candidates $A$ and $B$ can solve the problem is $\frac{1}{5}$ and $\frac{2}{5}$, then probability that problem will be solved is given by $\frac{12}{25}$.
Reason $(R):$ If events $A \& B$ are independent, then $P(A \cap B)=P(A) \times P(B)$.

Answer

$(d) :$ Probability of solving the problem by $A \ B$ is $=1-P($ None of them can solve the problem $)$
$=1-P(\bar{A} \cap \bar{B})=1-P(\bar{A}) \cdot P(\bar{B})$
$=1-[1-P(A)][1-P(B)]=1-\frac{4}{5} \times \frac{3}{5}=\frac{13}{25} .$

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