For a synthetic polymer, polydispersity index (PDI) value is 1.15, if the number average molecular weight is 40,000, then the weight average molecular weight of the polymer is

We know that, 

$$\begin{gathered} PDI=\frac{\text{ Weight average molecular weight }}{\text{ Number average molecular weight }} \\ 1.15=\frac{x}{40000} \\ \mathrm{X}=46000 \end{gathered}$$

Thus, weight average molecular weight = 46000

Hence, option (A) is correct.