The half-life of helium-5 is 7.6 × 10^{-22} seconds, and the half-life of helium-9 is 7 × 10^{-21} seconds.
Approximately [tex] \dfrac{7 \cdot 10^{-21}}{7.6\cdot 10^{-22}} = \dfrac{7}{7.6\cdot 10^{-1}} = \dfrac{7}{0.76} =9[/tex] the half-life of helium-9 is greater than that of helium-5.
Answer: 9 times.
