Question

What is the value of r

Answer 1

`{\Large \begin{array}{llll} B(d)=60000r^{(d)/(7)} \end{array}} \\\\[-0.35em] ~\dotfill\\\\ \begin{cases} d=7\\ B(7)=38487 \end{cases}\implies 38487=60000r^{(7)/(7)}\implies 38487=60000r^1 \\\\\\ 38487=60000r\implies \cfrac{38487}{60000}=r\implies 0.64\approx r`

now, we could have used d = 14 and B(14) = 24634, the value would round up to be the same.