In an ore containing uranium , the ratio of $\;U^{238}\;$ to $\;Pb^{206}\;$ nuclei is $3$ . Then calculate age of ore assuming that all lead present in ore is final stable products of $\;U^{238}\;$ . Take half life if $\;U^{238}\;$ to be $\;4.5 \times 10^{9}\;$years

Question

$(a)\;2.12 \times 10^{13} years\qquad(b)\;1.26 \times 10^{7} years\qquad(c)\;1.87 \times 10^{9} years\qquad(d)\;3.2 \times 10^{10} years$