The 238U isotope has a half-life T238 = 4.5x109 years and the 235U has
T235 = 7.0x108 years. N238(t) is the number of 238U nuclei at time t and
N235(t) is the corresponding number for 235U. The relative abundance r(t)
is defined as r(t) = N235(t). At present, r = 0.0072. Estimate the relative N238 (t)
abundance of these two isotopes 109 years ago. You might use the following approximations: ex 1+xforsmallx,e2.7andln20.7.

Question

The 238U isotope has a half-life T238 = 4.5x109 years and the 235U has
T235 = 7.0x108 years. N238(t) is the number of 238U nuclei at time t and
N235(t) is the corresponding number for 235U. The relative abundance r(t)
is defined as r(t) = N235(t). At present, r = 0.0072. Estimate the relative N238 (t)
abundance of these two isotopes 109 years ago. You might use the following approximations: ex 1+xforsmallx,e2.7andln20.7.